unless.....
they have made updates to more than just the processor and are going to hold a media event of some sort
Well we already know about the processor and multitouch trackpad, but more than likely that is going to be it (no new chipset = no redesign).
I would bet that in addition to the public iPhone SDK release, they are going to release something to let developers take advantage of the new multitouch trackpads in their notebooks. If that's the case, they would want the new MBPs to already be readily available so they can tout that to the press.