A Piper Jaffray analyst puts the probability of an "ultra-portable" MacBook being introduced at MacWorld at 85%.
That's as close to being a certainty as anything rumored to be about to sprout forth from Apple ever is, which is to say don't count on it until you hear Steve Jobs say that it's true, but be listening for it.
So what, you say?
Well, if the possibility of Apple bringing out such a device hasn't got you on the edge of your seat, you either never leave home (and hence have no use for portability) or you're underestimating Apple.
When Apple brings a new product category to market it represents a careful examination of the uses that device is likely to be put to, and typically a novel design, with a feature set that provokes first surprise then recognition, as the logic behind it sinks in and you realize that they've nailed it again. Apple hardly ever goes to market with a new product unless it's that good.
So, assuming that an 'ultra-portable' MacBook is a sure bet not to be an exception to that pattern, and giving the Piper Jaffray fellow the benefit of a doubt, there would seem to be something very special about to arrive, something that will at least reshape, if not redefine, portable computing.
And, as always with Apple, the truth may turn out to be even more interesting than anticipated.