I'm going to say I disagree. Apple learned few years back that doing a software and hardware rollouts at the same time is not a good thing. New iPhone + iOS + mobile me + mac hardware... it was not pretty and Steve was pissed. That's just my two cents.
Hmmm I could see this being a good point. If they bring out a redesigned MBP as well as a newish OS, now they might have to deal with potential design problems as well as software problems.
It would be like if the iPhone 4 not only had the death grip "issue" but there was also some problem with a new iOS released at the same time.
They could always get the computers out early, and offer a free Mountain Lion upgrade in the summer.