I'm very sure that this will be a GS remake. There've been all those hints through the ages, plus the fact that they have gold and silver party balls when telling us that they're gonna announce a new title? I kinda fail to see what else this could be, it's a little too soon for anything 5th generaton TBH. Plus, didn't they say that this would be a much-talked about title? Look at the internet. Seriously. There is GS remake speculation EVERYWHERE (and I must admit, I'm not exactly helping matters, I'm speculating it as much as everybody else!). I firmly believe that if you got together every Pokemon fan with internet access and asked them what they'd like to see next as far as a new game, at least three quarters of them would say GS remakes.
So yeah, I think it'll be GS remakes. I know nothing's confirmed yet, and I am not pretending otherwise. Just saying what I gotta say.