Haswell is the latest in the continuing parade of "next great things" that is the hallmark of the computer industry. To those of us who have been watching this parade for a few decades now, it's become comical.
Haswell is expected to begin to be released mid-2013. Intel usually rolls out server versions first, though that may change. I'd expect Apple has prototyping silicon now but I wouldn't expect to see a MacBook Pro using Haswell architecture until late summer at the earliest.
There will ALWAYS be some "next great thing" looming in the computer industry. The only sane way to approach decision making is this: Do you have a need now that can be fulfilled by a product you can buy now? If so, buy it now. The productivity you'll lose trying to buy exactly the right product at exactly the right time will be enormous.