I strongly believe Apple will do what they did with the Air last year and this year: release a great new design with existing chips only to update it a few months later with state of the art chips.
It all adds up:
1. new 15" Macbook Air spotted this Summer (which is actually the new 15" Macbook Pro)
2. a modest upgrade of the intel chips
3. the start of the holiday season
It would be a fitting tribute to Steve Jobs who might not be around this time next year