Apple Expo in Paris is being held September 12-16, 2006. This event will most likely see the light of Macbook Revision B with the new Merom processors, and possibly MBP Revisions if they aren't already updated at WWDC.
However, my advice to you is don't wait. Get what you want now. As many people have already noted the minute you buy a computer it becomes obsolete. Technology changes so fast. Many people waited for the WWDC for many months, and what now? After the WWDC comes the Apple Expo, in just 1 more month and then there will be something else after that. The updates never stop and if you wait you will never buy anything. That's just my two cents.
As for the Merom processor, I agree that a 15-20% performance increase is not worth waiting for so many months, especially if youre going after a Macbook. If you're going to use your laptop for normal everyday college use and not extremely CPU intensive tasks I don't think it's going to make that much of an impact. I think waiting a few extra seconds for a certain program is better than waiting for a period of months and be without a computer, if you don't have one already.
That's what I think. However the WWDC is less than 10 days away, so it would be a logical action to at least wait till until after that. In any case apple has been known to include the bumps and upgrades after 1 or 2 weeks of their major events, so you might just not see anything at all at WWDC.
My advice, If you absolutely can't wait, go for it. If you can manage it, at least hold on till a few days after August 11th.