MWSF is so close now and while I think an Intel PB announcement is unlikely there, you should at least wait and see what is announced at that event.
Otherwise it's a tough call. I almost always tell people "if you need it now, buy it now - there's always something new coming." But that is a bit simplistic in this case. You're buying right at (or very near) the end of one product cycle, and thus just missing the start of another. In the case of incremental upgrades such as the last 2 or 3 PB revisions, that's not a big deal. But in this case, the Intel PBs are expected (speculation) to offer significantly better price/performance and power consumption. That also likely means a PPC PB will drop in value much more than for the last few revisions.