Switch to a Mac has performed the old Macrumors trick of predicting Apple releases based on when the product was last updated, and according to their research, we're supposed to see new MacBooks and MacBook Pros before the holidays. On average, they're seeing just under 200 days between releases for both, and so they expect updates to the line before the end of November.
If you want my professional opinion (and I'll assume you did because you came here to read it), that's all bunk. I waited months and months while Macrumors' page said "don't buy - updates soon" on the iPod, hoping against hope that I would be able to get an iPod with a touchscreen, and it was just days after I finally broke down and bought a Video iPod that Apple announced the iPhone. I have no doubts that there will be a portable update soon over at Apple (in fact, I know that someone over at our sister site Engadget is waiting until January to buy an iPhone just in case there's a new revision announced soon), but I would say that before the end of November is a little too soon.
Still, if you're planning to buy a new MacBook or Pro and can stand to wait a few weeks, you just might want to. As usual, we guarantee nothing, and personally I doubt it'll happen, but if Switch's reasoning seems sound to you, give it a week or two and just maybe you won't be left out in the cold if Apple launches new MacBooks in early winter.
Update: Figures. I have to wait months for a new iPod, but when I post my doubts about using the same system to predict a MacBook update, I'm way wrong. And the Pros got updated, too. Good times.