Update: LR5 beta is out, so it's probably just a few weeks until v5 is available. I'd wait for that rather than buying LR4 now and then upgrading to LR5 a short time later
Sent from my mobile. Typos are a feature, not a bug.
Spoke directly with Adobe, no guarantee on delivery date for LR5. Beta 5 trial expires in June and according to Adobe: "If history repeats itself after a beta version expires, it is usually a month after that." Therefore I assume Julyish.
Here is some more stuff that LR5 Beta can do:
[video=youtube;Xo_FmVVa30E]http://www.youtube.com/watch?v=Xo_FmVVa30E[/video]