Don't quite follow that Kanto means no Sevii Islands - after all, they had been in FR/LG and suddenly the inclusion of the Kanto birds again gives them the possibility of having some point to them again. It's not that likely, but it can still happen. They can always come back with a 'point' to it as well - and they weren't even needed in FR/LG, arguably, so they could, if they wanted, but them in with little/no point. (Although if they are in I'd prefer them to have some plot or something there to hold interest for a bit. Like, say, the Kanto birds, and/or a subplot).
Furthermore, Kanto had been 100% confirmed a while back (a month ago?), along with that picture of the Magnet train. =P