I dunno, 4.9 on stock cooler means that we might be able to hit 5.5+ on aftermarkets... The new goal/standard will no longer be 4.0-ish but rather 6.0-ish. Quite the jump!
If this is all true then things look very exciting indeed and 2011 might yield better results than 1155
I heard that you hit the "wall" pretty quickly for Sandy Bridge chips. That is, your water cooling might be 10% better than air, your single stage vapor will be no more than 10% better than water, and cascade or LN2 not much better than cascade.
It's not the removal of the excess heat that is the real stopping block, it's the inability to push it any faster without wrecking the whole thing since so much stuff is tied to the clock.