Retina MacBook Pro review as a Mac Pro owner
Good read. This is the part that stood out to me, and it's a certainly part of the reason I'm waiting for now to upgrade:
We’re obviously in the middle of two awkward transitions: toward all-Retina screens, and toward all-SSD storage. The difficult computer choices that many power users will struggle with will probably be much easier in 2–3 years, when even the most die-hard desktop users can probably get a MacBook Something with a priced-within-reach 2 TBSSD and an external 27” Retina Display for desktop use.
I'm not going to wait another 2-3 years, but I think the next revision is probably going to be the right time.