but would it kill him to have an announcement that new MPs will be released in 1 or 2 or 3 months?
That approach has killed companies before.
http://en.wikipedia.org/wiki/Osborne_effect It would not likely literally kill Apple, but it is not a best practice business wise. Apple is being very disciplined. No exceptions (unless extreme circumstances) to commenting about stuff in advance. If there is a very simple rule then it is easier to make everyone follow it.
[ although it appears they do leak stuff if going to get a positive spin. However, that appears to be reserved to building hype, not being informative. ]
If there was some single customer who was going to buy $10M of MPros or walk in the next couple of weeks, then probably could get a NDA briefing. Someone who is going to buy 4 orders of magnitude less product won't.
Remember how far in advance they announced the iPad 3G?
Comparing apples and oranges. New, never been released, product lines get a lead time to introduction. Even more so when have to get FCC and/or external vendor testing, need to ship new SDK early to entire developer network, etc.
This is a product update on a mature product line. There have been the equivalent of a MacPro product for over a decade. There is no huge tectonic shift; just a regular update that happens to be quite late.
Several years ago Apple used to occasionally do an intro at a MacWorld and the shipping date would turn out to be a month (or at least several weeks) later. That was done in part because needed "ooooh aahhh" content for a fixed in stone date. They announced, along with dropping MacWorld, that they would do announcements on products as the were ready instead of readjusting the product release drops to fixed dates. Perhaps that really just should have said dropping Mac product announcements with fixed dates.
The ipods always drop in Sept-Oct for Christmas rush (Apple still doesn't have enough juice to move Christmas day and rest of holiday season. LOL.). The iPhone seems to be adjusting to drops in June so can do dog and pony show at WWDC. However, some stuff like iPhoneOS has moved out of fixed dates also.