The next release is tied to Intel's Haswell release. Current rumors put a Haswell release around June 1st. Expect a Macbook refresh a month or two later.
Thank you thank you thank you!
I am so sick of hearing that the Haswell Mac's are coming out the first week of June. Apple has NEVER been that fast. Typically, it's two or three months after the release of a new chip that Apple starts rolling out new models. Intel doesn't exactly have a great track record of releasing on time either.
Personally, I think mid-July will be the EARLIEST you'll be able to get your hands on a Haswell MBP. I don't think even as late as October is unreasonable (based on both Intel AND Apple being on the later end of their release track record). Though most likely release Window, IMO, is mid-July to mid-September.
So, OP, if do just what it says. If you need it, buy it! It'll still work 6 or 8 months from now.
But, 6 months from now Intel is going to be releasing a new chip (based on leaked timelines by the way, I don't think they've actually announced a release so far), and Apple will have it in the rMBP within a couple months beyond that, so that's where we are!
I'm not losing any sleep over buying a MBP a few weeks ago. 6 months from now I'm only a year away from Broadwell! It gets Silly. Tech moves, what you've got is gonna be outdated. Just buy what you need and upgrade when you're ready. Haswell is going to be pretty incremental honestly. Intel said the focus is power consumption, not necessarily performance. So perhaps a bump in battery life (or if Apple chooses, a slight reduction in weight if they use the juice-equity nabbed in the new lower power chips to shave the battery a bit smaller and still keep 7 hours of battery life), though a significant bump in performance (like HD3000 to HD4000 graphics or Intel Core 2 to i5/i7) is not likely this time around.