It feels like its time, and considering they'll most likely hold off on the new iPhone 5 till late fall like last year, it seems to make sense to introduce new MacBooks considering the discussion of OSX Lion; hardware and software married together once again.
Further, seems like if new MacBooks are introduced during WWDC then it would only help drive huge sales during the summer and even more so when back to school fall rolls by.
Further, seems like if new MacBooks are introduced during WWDC then it would only help drive huge sales during the summer and even more so when back to school fall rolls by.