Personally, based on rumors about development starting this year, first next-gen versions of Unreal Engine being discussed, and a next-gen title should take at the very least 2 years of development, probably 3, I would say that we're still at least 2 years out, so I would be quite surprised if we get something next year. If we do get something that soon, it would only be in reaction to the Wii U, but even there I feel it would be safe to have the Wii U on the market for one year. More important would be to release at a good price-point versus the Wii U, which the inclusion of the tablet may well help with.
So the only reason Microsoft would go for it would be because Sony couldn't follow, as that year they'd still be way too busy with Vita. Microsoft is comfortable in the US right now, and the other regions show less indication of being ready to move to the next-gen consoles imho. On the other hand, I do think that some publishers are very ready to move on and revitalise their franchise sales with next-gen versions.
But I don't know if the consumer market is ready for it. But on the other hand, I'm fairly sure they'll be ready for sure within two years. And here of course I'm talking about the group of gamers that buy the first 15 million.