WiiU 2012
PS4 late 2012 -2013, remotely 2014
X720 2013 with the launch of Halo 5? and Kinect 2.0,
I think MS will be most likely the last in the race, and with possibly Sony will come out around the same time. Sony's current troubles are certainly going to slow the release of the PS4. I think much of it will depend on how well the WiiU does or doesn't do.
If the other HD consoles can still sell well against it, why come out with a new expensive console? If the new Zelda was coming out exclusively on the WiiU then N would really have something, but I don't know what major games are going to push the brand.
MS wants to continue to expand on Kinect and as long as they can compete well. There seems to be no reason to upgrade, plus if the Kinect with other languages starts working well with the new dashboard. It could really boast sales in Europe and elsewhere.