@Johnny
The only reason I disagree with that possibility is at least for the 360 it would alienate the earlier purchasers. If developers made a game to fit on a Blu-Ray, only those new console owners could play it.
There will probably be revised systems that are smaller or "slim" coming out in the next year or so, but no real revisions to the internal hardware. Those major revisions will still wait for the next generation I'd say.







