My expectation about Modern is that for most people, changing archetypes is a slow process. It might be more accurate that most people have 2-5 decks they own and are comfortable playing and choose which one based on how they're feeling or what they expect. In general, this means people adjust to changes in the Modern metagame slowly, which is actually appropriate, because the Modern metagame correspondingly changes slowly.
For most people, the last week before a tournament is likely a matter of changing your last few cards - the things you view as flex slots in your maindeck and sideboard, rather than a scramble to decide what to play the way teams are used to in the days leading up to a Pro Tour.
My more specific expectation about #SCGINVI is that people will be relatively flexible, fast to adapt to new strategies, and extremely aware of the results of #SCGBALT, as well as most articles on this site, like this one. This means that if you're preparing to play Modern at SCG CON Winter, you should expect Arclight Phoenix's presence to be more impactful for the format as a whole than if you're playing anywhere else (except maybe Magic Online, where things also change very fast). That means both more Arclight Phoenix players, and, appropriately, more hate for Arclight Phoenix. It's interesting to me that all the incentives just happen to line up appropriately naturally in this regard, so there's not really much you need to do to account for it, at least that's my first impression.