Sounds to me like this is going to be the first Console specific Unreal engine. While Unreal 3 has performed well on 360 and pretty well on PS3 (after a lot of tweaking) it was, after all, more of a port of the PC engine than anything else.
So I'd imagine it's a case of get the engine ready working closely with MS and Sony (maybe Nintendo) for the new consoles and get it to developers as early as feasible, which could me a year or more before the consoles actually launch, to ideally get as many on Unreal 4 as possible working on launch titles.
I'd imagine they'll either then bring Unreal 4 over to PCs afterwards or produce Unreal 5 specifically for PCs.
So that would mean 2013 maybe 2014 for the next consoles (assuming my assumptions are actually correct).
Depending upon how well ID tech 5 goes when it launches with Rage and of course the new Cryengine with Crysis 2 developers are going to be spoilt for choice for high end middleware optimized for consoles - which is good for development costs.
Try to be reasonable... its easier than you think...
