Well, my thoughts on the subject is that it's not just a matter of what the hardware manufacturers think, but also what people are willing to endure. The economy isn't exactly in great shape and people don't have massive amounts of spending money. Getting people to shell out a few hundred dollars on a new game box doesn't seem all that likely to happen.
On top of this I notice that Sony seems to be getting all hot and bothered to start recycling various PS-2 titles to the PS-3. That doesn't strike me as the kind of move they would be making if they plan to retire the PS-3 in a couple of years.
What's more, if developers are to be believed they can't even really use the current consoles to their full potential, so why do they need a bigger and badder generation? I mean one of the claims by Squeenix was that they couldn't make "Final Fantasy VII" with this current generation of hardware because it would be too expensive to produce all that content. One would expect they would want to get the current hardware under control and "Tamed" to the point where they can produce those kinds of quality titles efficiently, as opposed to coughing out another, even more advanced console that will be even more expensive to work with and wind up regressing things back even further.
I mean heck, now all these years into these consoles we still have people complaining that the majority of titles look they they could have been produced last gen (and to be honest a lot of them probably could have been), it's relatively uncommon to see someone talking about how a game really takes advantage of the current hardware...
The bottom line is that I don't think we'll see new consoles in the next couple of years. I mean I could be wrong, but it doesn't seem likely given that these don't seem to be fully tapped/exploited yet, and the simple fact that I don't think all of the current millions of people with consoles in their homes right now have a few hundred dollars they can just decide to go out and blow on a whim. Of course I could be wrong, we'll have to see what happens.