I've seen lots of threads lately on what people want to see, what people expect with the next and future expansions, and also what the loss of subs means in regard to the lifespan of the game. I also haven't seen this idea (not that I pay much attention).
An expansion down the road, where Re-Origination occurs. It would basically be what happened with FFXIV.
A complete overhaul. A new game. A new graphics engine. A lot of similar concepts, but new classes, new places, new abilities, a completely redone history and past. Of course, this would be a massive undertaking, and would require likely an entire department, like Titan has. It couldn't just be a simple 'next expansion' thing. I would expect it to have 3-4 years of development behind it.