I do not think they will release a new one anytime soon, I they they anounce someting in the near future just to get some buzz going but like someone said they are still making big bucks off the 360..
Well, if they take 5 years to develop, then they definitely start a good amount of development before announcement. I think the original plan was to have the 360 as their console for 5 years, meaning the next one was originally planned for 2010. However, companies never stick to these deadlines, and I think now they are shooting for a 2012 release. That makes more sense I guess. 5 years is a bit short for a console life, don't you think?