Well if you watched the Macworld Keynote you know that there will be no 12" MacBook. Why? Because Steve Jobs said so. When he was leading into his intro of the "Air" he stated that other manufacturers compromise their sub-notebooks by giving them 11" and 12" screens. So Mr. Jobs thinks that the 12" form factor is a bad thing and would "compromise" the MacBook. Regardless to the fact that many people who have 12" Powerbooks have them because we WANT the "compromised" space and many of us have in fact gone from larger PowerBooks to the 12", Steve doesn't like it and what Steve doesn't like doesn't get made.
Steve also knows that all of us holdouts will eventually have to fold as batteries die, and new "gotta have" apps come out as Intel Only apps and of course we get tired of the 1.5 Ghz processor that the last iteration had.
Yes, the 12" Powerbok is dead and the prospects of a new 12" model has just been buried. Enjoy yours while it works.