That's if they don't keep those locations locked up...like say a secret part of the Petalburg woods we can't access until post game, etc. Though again Eevee isn't even a Hoenn pokemon so that'll be how it'll work (strangely B2W2 had the locations restricted until post game places despite all eeveelutions being in the dex). If anyone is added it'll proably be Magnezone. Roselia proably won't be able to get the stone needed until post game...
Also does anyone think there'll be a mission post game to trade with BWB2W2 like there was one with FrLG and RS. It's possible seeing how Unova is so far away...they could make us establish a far distant link using a Black Stone and White stone etc.
Also I wonder how we'll get the DNA Splicers in game for the new Kyurem forms...I guess Drake could give them to us, or perhaps they'll be in Meteor falls in a secret room (the last one seems most possible to me), maybe Kyurem can be in game too through an event like how DPG can be obtained through the Arceus event.
Ps: Does anyone see GF adding any new forms? FrLg were the only remakes thus far to introduce a new form (Deoxys A and D forms) so it might happen again...though I heavily doubt it.