If you were considering buying a 15-inch MacBook Pro within the next few weeks, you may want to hold off because its almost upgrade season.
Gizmodo has a pretty good write up on what we can expect from the next version of the Pro, and much of it is pretty obvious: A solid state drive, an absent optical drive, and a flashy display all seem to be fairly certain features, but what really excites me is this: A 15-inch MacBook Air would finally bridge in the MacBook line the gap between the fully functional and the highly portable.
Right now, if you wanted to buy a MacBook, you'd have a five choices: the 13-inch, 15-inch, and 17-inch Pro models, or a choice between the 11-and 13-inch versions of the Air. For those regularly on the go, the 17-inch Pro makes zero sense, so that gets eliminated as a possibility almost immediately. Same thing goes on the opposite end for the 11-inch version of the Air, which has always struck me as being a bit too small to be useful on its own.
That leaves you with the 13-inch and 15-inch MacBook Pro and the 13-inch Air. The 13-inch Pro isn't awful, but nearly all of what it does is done more effectively by the 13-inch Air, so we will eliminate that as a possibility as well.
This is where we find the sweet spot for a 15-inch MacBook Air, right where the high-end Air meets the low-end 15-inch Pro. The device would be ideal for those who want the portability of the Air but aren't willing to sacrifice the screen real estate of the 15-inch Pro.
Sounds good, but what's the timeline? Decide recently changed its verdict on the MacBook Pro from a "Buy" to a "Wait", which is pretty good advice. The current 15-inch MacBook Pro was released in October 2011, making it five months old. With that in mind, a Spring announcement seems like a pretty sure bet.