Beyond the for-sure software updates, I think a 15-inch MacBook is one of the most credible rumors we have. Someone uncovered manufacturing contracts that evidenced this last month. However, I'm not sure where in the pricing lineup it would fit; I'd think they would have to knock the 13" MacBooks down $100 or so to make room for a 15" MacBook that wouldn't be too close to a MBP's price.