I don't see any reason why they'd ever stop.
And honestly - if I see one more person prattle on about whether or not you can trade from this gen to that gen, I'm going to reach through my monitor and slap him. Although that was something that was mentioned alongside FR/LG, I don't think it was ever the central issue, and it becomes more obvious with each set of remakes that that's not the point. The real point of the remakes, obviously, is to do updated versions of the older games on modern hardware, in order to appeal to fans who want to see the games they love take advantage of new technology. So stop it with the "but you can still trade this to that, then hook that up to the other, then blah blah blah, so they're not necessary" nonsense. Old games plus notably better hardware equals remakes.
Now - that out of the way - I would generally prefer a sequel or merely a return to the region over a true remake, just because I'd rather see a new story than an old one. Yeah - a true sequel would be sort of disconcerting for people who hadn't played the original games, but it's easy enough to do a sequel that has enough references to the past story to amuse those who did play it, but is separate enough that not having played it isn't a problem (and that's pretty much what they did with BW2, so we already know they can do it).
So - I fully expect a return to Sinnoh in the future, then a return to Unova, then a return to Kalos, then a return to... wherever the next new region is. But I wouldn't expect the Sinnoh ones for at least one more generation of hardware. It seems to me that while the 3DS is obviously advanced over the DS, there just haven't been enough improvements in the capabilities to make remakes worthwhile yet. And I think it needs to just languish a bit, to give the fan base time to really build up their appetite for the remakes.