I'm on the edge of buying a macbook myself, as an upgrade from my powerbook 15".
Only thing holding me back is the nagging sense that an update is immient.
I'd be happy with any one of the following:
- Updated graphics e.g. the integrated X3100 (for future proofing)
- LCD screen (cheaper for apple than putting it in the MacBook Pros)
- Santa Rosa (battery life extension!)
Then again, it could be not till next year

My sense of history tells me that if not in September, then it won't happen till next spring.
I feel that apple launches new models in periods of low demand (i.e. after the back to school rush, and after the xmas rush), maybe so that bugs can be ironed out with minimum fuss.
What do you think?