They are quite likely to "make a lot of sense" - also (or, particularly) with the launch of next gen in 2012/2013.
All those dozens of millions of installed, very capable systems (and in one case, still among the best Bluray players; in another, recently "uprated" with Kinect) won't disappear overnight, won't be replaced very rapidly by next gen. Particularly when the dynamics change: when systems became more connected during last gen, more relying on digital downloads (of all kinds, basically finally becoming the prophecised set-top-box bringing new level of music/Last.fm/films/Netflix/"new TV"), also with ~indy titles which are bound to be produced for a few more years; when the average(!! ...that means, typically, a laptop with integrated GFX) new PC only recently approached (according to Gabe Newell of Valve, for example) the GFX/gaming power of present console generation, when the capabilities of the latter don't yet really limit what's possible in game mechanics.
Really, there's no reason (whatever the angle - unnecessarily cranking up conspicuous consumption, or: it would piss off too many owners) to almost demand simply dumping this hugely valuable, installed base (laboriously built up over several years).
It's easy to imagine the present generation systems getting 3 or so years of quite decent support, after the launch of their successors. Sony basically did just that already with PS1 and PS2 (not MS with Xbox1, but they evidently wanted to drop this a bit flawed, when it comes to market practicalities, first attempt of theirs)
And so, next-next-gen will be probably in the 20s, in the third decade of this century... crap, I'm getting old.