Bike ≠ Car ≠ Ped.
Join Date: Jul 2007
Location: Washington, DC
Bikes: Some bikes. Hell, they're all the same, ain't they?
By "first quarter", I'm taking it to mean October 2009.
Everything I've seen so far points to 10.6 not being released anytime soon. It's hardly been shown to the public, either. I'd expect the first real look to come at the WWDC in June, then the actual release sometime this fall.
Then, as usual, 10.6.0 won't be perfect, but they'll have most of the real-world tweaks done by 10.6.2, and that won't be until Spring 2010.
If you want a Macbook now, get a Macbook now. It'll run 10.6 just fine later on.