Personally, I'm expecting processor and RAM bumps either the week before or the week after WWDC. They're not going to devote the keynote to mere processor bumps, and I don't expect any revolutionary tech advances to the Macbook or Macbook Pro lines. We might see the Macbook Air mentioned at WWDC if it gets 3g, but I somehow doubt it. It will more likely be covered by a press release along with the other laptops.
WWDC is going to be devoted to the new iPhone, iPhone OS 3, and Snow Leopard. I don't anticipate anything else.