If one waits forever for because something new may come out, you will wait forever. If a new one comes out tomorrow, it will have a Freescale CPU, but in a few months after that one with Intel's new Mobile CPU that is due out next year will be here and you will be mad because you did not wait and after that a few months there will be another one with more changes. There will always be new systems with a few changes. If the Current PB will do the job for you now and in the future, I would just go purchase one. I got my Mini knowing full well there would be changes, but I did not want to wait forever for my new Mac.
If I was going to wait for a new PB it would be the ones next year with the new version of the Centrino, (forget the name right now).