From what little we glimpse from the trailer, it seems like Alola has got a little facelift. That path up Route 1 is now full of blooming flowers, and I don't think the player character's house used to have a surfboard? Hopefully, these games will do like BW2 and put little beautification improvements everywhere. Sun and Moon looked good, by all means, but it's nice to see each area get a little additional touch-up.
Also, seems like Totem Mimikyu is returning, and we might get Totem Togedemaru and Lycanroc as well. Time will tell what other Totems have been updated - or if the concept has been expanded or changed. I'm willing to guess it's the same as before, but you never know.
My guess as to when we will get more information is a more substantial trailer at E3. CoroCoro will drop in a few days too, but I think it will just rehash the announcement. Interestingly, E3 this year is June 13-15, which is right in the middle of the period between CoroCoro's usual leaks and its actual release. If TPC is savvy enough to realize that whatever is written in CoroCoro will be spread all over the Internet two days before Nintendo's scheduled E3 conference, they might not give the magazine any exclusive news this month, not even a summary of whatever they release during E3 (if anything). Then again, the fact that CoroCoro has leaked on the 10th or 11th with amazing consistency for the past several years seems to have escaped them completely in the past.