think the last week of winter regionals has the same format as the first 2 weeks of spring regionals (not sure when in there generations became legal so that might be a change) so the top decks for that and states are a good indicator.
if your regionals is the week of may 28 Fates Collide should be legal so it's hard to say how it changes the format as we haven't had any big tournaments with it yet.
this should let you look at the decks that have done well in states/regionals, don't think the meta has changed too much been yveltal/dark, night march, seismitoad, vespiquen and a few others for a while now.
I figured it would change some due to being expanded but wasn't sure...so the regionals I plan on going to is May 21, fates collide won't be legal for that format?