Most of the mac rumors that I have read, have, indeed come to pass
I'll admit, about 15 years ago I thought the same thing. Then I started to really read those "prognostications" and found that they really don't tell you much of anything. They don't come from Apple. They are from market analysts, investors, tech-bloggers... basically from anyone BUT an actual source at Apple.
In the calendar year 2005 to 2006, rumor sites scored about a 30/100 (and that is being very generous). In all, they scored:
11 partially to mostly correct predictions
8 completely incorrect predictions
11 completely missed announcements
In a total of 30 situations, they only got 11 of them partially to mostly correct. Rarely, if ever, do they get anything spot on. You can also see that for everything they got "correct" (I use the term loosely here), they completely missed something else all together. In short, their odds of getting something right are no better than simple chance... and that is pretty much par for the course.
So... in all my years of using Apple products, watching Apple release products, and hearing about the crazy rumors and predictions people come up with about Apple releasing products... the rumor mills get it wrong much more often than they get anything even close to right. That being said, I can say with at least some degree of knowledge and authority that rumor sites are mostly crap.