Microsoft may be rushing the next gen out in 2012.
If the Xbox 3 is coming out in 2012, I'd hardly call 7 years for a successor to the 360 "rushing". This console cycle has actually gone on pretty long.
Microsoft stated last year that they expected the 360 to flourish until 2015. They are also releasing Halo 4 in late 2012 on the 360. If they had planned on releasing a new console in 2012 don't you think they would have wanted the new Halo trilogy to sell their new console? They see they are losing the lead they have over Sony and know if they want the next gen to go as well for them as this gen they need to release the next xbox before the next playstation. It may have all been a big conspiracy to try and pull a fast one on Sony but if you take 3 years off the expected release date in less than a year it sure sounds like trying to rush it to the market to me.
Them saying they expect the 360 to be viable for until 2015 doesn't mean that they won't release a successor before that much the same way the ps2 remained a viable platform at least 2-3 years into this console generation. Sony also said that they expect a 10 year lifespan for the PS3 but also say that that a successor would be released before that 10 years is up. Generation overlap and transition has has always been a part of the business.