It seems likely that there will at least be a small bump anytime now, but I still went ahead and bought a MBP yesterday. I had wanted one since last January, but wasn't ready to purchase until later in the year. Then, I decided to wait a few months until MWSF for supposedly great updates. I'm very disappointed none were announced, but for me, the current 15 inch, 2.6GHz, 200GB HD is more than enough to fit my needs. The more I thought about it, the only update I really wanted was a better graphic card, but that seems unlikely anyway.
My advice, if you really want/need it now and the current specs seem ample to you, go ahead and buy. If you're worried the current specs won't be enough for you in the near future, wait. However, besides a redesign/aesthetic changes, it's my understanding none of the speculated updates will significantly increase actual performance, especially for someone who, like myself, doesn't use many intensive applications. If a redesign is terribly important to you, you may be better off waiting, but there is no guarantee that a redesign is imminent. If you're worried the current specs aren't powerful enough to handle your current tasks, you may be better off not getting a MBP at all.
Nobody wants to shell out thousands of dollars on a product that gets updated soon after, and I'll admittedly be aggravated that I didn't wait another month if it gets updated by then. However, I dig everything about my purchase and I see it doing everything necessary for the next few years.
Just my two cents.
