OK, but that's 6-7 out of over 100,000 MacRumors members...
The number of ACTIVE users is less than a quarter of the 120k signed up here at MR. Hell, the max users ever online at one time was only around 9,000. Let's say the number is 30,000.
What about people who don't post? What about guests?
EDIT: I should point out that guests ALWAYS outnumber members. At this moment there are 164 members logged in and over 1200 guests (1200 / 164 = 7.3)
Well, let's assume you're right and mac rumors posts are an accurate measurement (which it is not). That would mean 7 out of 30,000 mac users are waiting for the mac pro.
If there are 22 million mac users worldwide (22,000 / 30) * 7 = 5,100 users waiting. There also a large number of people who will hear about the new specs of the MP and buy one based on that, as opposed to sitting around and waiting for it to be updated. I would conjecture that the 'casual' buyers are going to outnumber people who are waiting. They're going to see the new mac pro specs and decide that they want one.
Again, it is really stupid to say the number of people waiting here on MR are a proportional representation of reality. The reality is that bulk shipments are waiting on the new version as well as the tiny portion of people waiting around here.
The Mac Pro, especially, is bought by PROFESSIONALS. It's a demographics issue: Different people, in general, buy the Mac Pro than buy any other Apple machine.
Most people who are going to buy a mac pro have real professional and social lives and wont spend them posting "OMG I WANNA NEW MAC PRO GIMME" on a forum, especially since it does nothing but pass the time.