Scrow said:pretty much. let the market decide where it goes.
on another topic, here's my prediction for blizzard's release schedule in the next few years (optimistic).
SC2:WoL - March-May 2010
WoW:Cat - November-December 2010
Diablo 3 - Feburary-May 2011
SC2:HotS - October-December 2011
SC2:LofV - October-December 2012
WoW:Xpac4 - Feburary-May 2013
beyond that... who knows? New MMO late 2013, early 2014?
Blizzard's approach for WoW has been to try to reduce the length of time between expansion packs, not increase it:
Vanilla:
Released: 23rd Nov '04 (NA), 11th Feb '05 (EU)
Burning Crusade:
Announced: Oct 28th '05 (1 year after NA release - wow, was it really that early?)
Released: Jan 16th '07 (1.25 years after announcement)
Total time: 2.25 years.
Wrath of the Lich King:
Announced: Aug 3rd '07 (0.5 years after BC release)
Released: Nov 13th '08 (1.25 years after announcement)
Total time: 1.75 years.
Cataclysm:
Announced: Aug 21st '09 (0.75 years after WotLK release)
Released: ???
While you could make the argument that they always release 1.25 years after the announcement - since that is the most consistent factor - I think that's misleading due to the fact that the more recent announcements have been around Blizzcon; it makes rather more sense to handle the things at a large event like that. If we're looking at the same turnover time as Wrath had, we'd be looking for a release next August, but since it's trending to a shorter development process, I'm still reckoning we'll see Cataclysm earlyish next year (before SC2? Quite possibly). Two years to Pack 4 seems especially unrealistic.
Also in favour of that is the 'remaining content' argument. While they could always add a Sunwell, potentially, to fill in any large gaps in time, *currently* we're on course for a brief celebratory visit to Onyxia (not, it appears to Blizzard, regarded as a major raid, just a bit of birthday fun), then Icecrown, and then we're done with Northrend. Given that we've had a new major raid every 3-4 months - Blizzard's own effort to avoid the massive gaps without a new raid that were problematic back in TBC - it's worth bearing that patch release schedule in mind when planning out when Cataclysm will hit.