I highly doubt RSEmakes will happen in gen 5. Pokemon needs to move to the 3DS. Our next titles will probably be gen 6 after a decent wait, and I'd honestly be okay with that. RSEmakes on the 3DS will be far better than if they were on the regular DS family. I see no need to rush.
Granted, they definitely will happen. There really is no reason why they won't. As more and more people move towards the 3DS, there will be no way to transfer gen 3 games into gen 4. And even if we aren't in gen 6 yet, you'd still have to transfer to gen 4 and then into gen 5--combine this with the lack of GBA slots and you've got yourself one large inconvenience.
Also, I feel that RSEmakes are being hinted at in the same way that GSC remakes were hinted at. Dive, old music sections being thrown into new music, small references...yes, I know gen 4 was referenced more than gen 3, but that's because: 1. Gen 4 is closer in time to gen 5, and 2. These are supposed to be hints, not blatant announcements.
There are a lot of gen 3 legendaries becoming available, but that still leaves the vast majority (the non-legendaries) to be caught.
Also, a fun little fact: all gen 3 Pokemon got completely new sprites in BW. With the exception of gen 5 (which doesn't even really count since they're all new Pokemon), no other gen got this treatment in BW. It honestly seems like Game Freak is preparing for something.