1. With the addition of Goblin Chainwhirler, Mono-Red Aggro is the Standard deck to beat at SCG Atlanta.
Matthias Hunt: Fiction. Standard has been a midrange format and I expect it to stay that way. Goblin Chainwhirler is a powerful card in a format where its enters-the-battlefield trigger can double as burn and removal, but with Standard where it is, I don't see it being removal very often. We're in a Standard format where text boxes on threats just don't matter that much. Fatal Push, Harnessed Lightning, and Essence Scatter all deal with this threat as cleanly as they dealt with the threat before it, and I don't see a 3/3 for three mana changing that math at all.
Ryan Overturf: Fact. Goblin Chainwhirler is the absolute truth. Triple red is a prohibitive casting cost, but Mono-Red Aggro just so happened to already be a great archetype in Standard. Cutting Sunscorched Desert is pretty easy, given that Chainwhirler deals one damage to your opponent when it enters the battlefield anyway. Cutting Scavenger Grounds is a little tougher, given the power of God-Pharaoh's Gift, though you often win fast enough to justify this and you also still have Abrade.
In addition to just being great against one-toughness creatures and a number of token generators, Chainwhirler also makes some good-looking blocks into terrible ones. Dominaria offers a lot of powerful options for deckbuilding, so it's hard to say that Mono-Red will be the best deck as the format is further explored, but it is both good enough and easy enough to understand that it should be out in force Week 1.
2. Given Matt Nass's third-place finish at GP Phoenix and win at GP Hartford, Ironworks Combo is the Modern deck to beat at SCG Atlanta.
Matthias Hunt: Fiction. What a world we're in where Krark-Clan Ironworks and Amulet Titan get to meet in the finals of a Grand Prix. Both are decks I've spent some time with, and while they can each catch a format off-guard, I don't think either of them is the type of deck that can push through hate.
As far as the modern metagame goes, Krark-Clan Ironworks is very similar in its position to U/R Gifts Storm. They both can win on the same turn with the same amount of consistency but fold to different types of hate. While I generally prefer Storm over Ironworks, the artifact combo deck will be better in a field where people are casting Fatal Push and Lightning Bolt.
That said, I expect people to adapt their hate to Ironworks. Cards like Rest in Peace and Stony Silence are very hard for the deck to beat, and if you want to beat all three of the decks I mentioned, Damping Sphere is now legal and can fit in any deck.
Ryan Overturf: Fiction. At SCG Milwaukee I had the opportunity to watch an Ironworks player go through the motions of comboing off, and it looked outright exhausting. Most players consider decks like this to be profoundly boring, and even if Ironworks were the best-positioned deck in Modern, it would be doomed to be under-represented due to its monotonous play patterns.
Hate cards against Ironworks, such as Stony Silence, are also quite powerful. I would expect that Humans will be the most popular deck in Atlanta. It has sort of been taking over the format lately. You can almost never make meaningful predictions about Modern just by looking at one weekend's results, and it is much more worth noting that Humans has just been everywhere for months.
3. With Deathrite Shaman still legal in Legacy, Grixis Delver is the Legacy deck to beat at SCG Atlanta.
Matthias Hunt: Fact. Deathrite Shaman is just the best card in Legacy right now and Grixis Delver is one of the best decks you can play it in. This has been the case for some time, and while Grixis now has more bad matchups than before – Magic Online is teaching us that – I still think it holds the crown of "deck to beat."
Legacy moves slowly. For the player who knows Legacy in and out, I expect that they may play a deck like Four-Color Leovold that is even better at playing fair than Grixis Delver, but Grixis can even win those matchups if it has to. I'll call it the deck to beat and would be surprised if there weren't at least two copies of it in the Top 8.
Ryan Overturf: Fact. I personally believe that Grixis Delver is slightly overrated, though I can't deny that it has been the winningest Legacy deck as of late. I buy that it goes at least even with the Four-Color Control decks that try to go over the top simply by being leaner, though I feel that the Miracles and Lands matchups leave something to be desired. It's great at beating up on the field, though, and has the tools to beat anything. Grixis Delver will in all likelihood be the most-represented Legacy deck in Atlanta.
4. You expect at least one copy of Teferi, Hero of Dominaria in the Top 8 of SCG Atlanta.
Matthias Hunt: Fiction. I wish, but it's just too crowded at the top. Teferi is a powerful new planeswalker and I actually expect that we'll see him on camera this weekend, but I'm not ready to say that he'll go all the way to the Top 8. There are just a lot of great mythics out there that we can cast. Karn, Scion of Urza and Yawgmoth's Vile Offering now join the already-great cast of finishers in The Scarab God, Torrential Gearhulk, and Liliana, Death's Majesty. With all this at the top, I'm just not seeing a place for Teferi just yet.
Ryan Overturf: Fact. Various U/W decks have already been putting up 5-0 results on Magic Online, and Teferi tends to be a common thread. I'm honestly not sure which card is better in the heads-up comparison between Teferi and The Scarab God, but either way, U/W looks like it has surpassed U/B on power level in Standard.
Seal Away is a major contributor here, as is Raff Capashen, Ship's Mage. Having access to a great two-mana removal spell with flash is a massive upgrade, and the play patterns for Raff alongside cards like Lyra Dawnbringer put your opponents in really rough positions. Todd Anderson had great things to say about these decks yesterday, and I agree with him on all counts.
People were winning matches with Approach of the Second Sun before Dominaria with decks that were pretty horrendous. Winning matches with a card as powerful as Teferi should be extremely easy by comparison. It wouldn't surprise me in the least to see two Teferi pilots in the Top 8 in Atlanta.
5. You expect at least one copy of Mox Amber in the Top 8 of SCG Atlanta.
Matthias Hunt: Fact. It's a Mox, and despite the drawbacks, every Mox to date has seen cross-format play. What I'm not sure of is which format we'll see Mox Amber in. Standard has plenty of legendary creatures and planeswalkers right now, so it wouldn't be surprising to see Mox Amber sneak into some of the lists as a way to get ahead on mana in the mid-game. On the other side, Modern is the format where decks try hardest to avoid interacting with their opponents, and a Mox is a great way to do that. It isn't clear, however, if any deck in Modern is ready to slot Mox Amber in.
Despite all of these question marks, a zero-mana ramp spell is just too powerful to ignore and I'm sure we'll see something this weekend.
Ryan Overturf: Fiction. This call is a little tougher, and if I have to commit, I'll take the coward's route and call Fiction. Mox Amber has met fairly mixed reviews so far, which is understandable. It's not a true Mox in the sense that it will let you cast two-mana spells on Turn 1, but mana advantage is too powerful to dismiss just because it's not completely broken. It would not surprise me in the least to see Mox Amber in the Top 8, but the reason that I call Fiction is that the Mox Amber decks are just harder to figure out than decks like U/W Control and Mono-Red Aggro.
Standard is pretty large right now and plenty of viable decks already exist. Mox Amber asks some novel questions that are tough to figure out on Week 1. How many enablers do you need? What mana gap are you trying to bridge? Is there a combo payoff, or are we just going big? Do you actually want the full four Moxen? There are a lot of cool options, and I would expect at least one type of Mox Amber strategy to break through inevitably. I would just bet against it on Week 1.