I'd say this isn't worth it unless yet much cheaper.
You gain 2 cores and a bit of cache.
OC will be a little harder so eventhough the process is smaller (at 45nm),
your final oc might not be bigger than 3.8Ghz.
The gain from the extra cores will be noticeable but not ground breaking.
So I'd wait it out.
This is assuming that Ivy Bridge will indeed allow for meaningful bus overclocking.
So far I've read that BCLK can be stepped with IB, giving you a base of 100, 133, 150mhz and so forth.
But here's the catch:
What's holding Intel from also lowering the CPU multiplier range when it detects a higher BCLK?
I'm sure they can think of a reasonable explanation for that, and I'm sure they're considering it ><
3.8GHz on a Q9650 is effortless and not to mention is has a higher multiplier than a Q9550, so 4+GHz is within reach unless you have one crappy motherboard. Also, heat is not an issue with these Q9xxx series because they're using 45nm. When it comes to pcsx2 it's just a few hundred megahertz apart to match a Sandy Bridge CPU. I will continue to use my Core 2 Quad system until Haswell is released simply because the Q9xxx performance doesn't disappoint me.