While the Apple employees that I spoke with today were mum about an eventual non-glossy version of the 15" MacBook Pro, a company called TechRestore has taken matters into their own hands, and is offering a $199 conversion:
Apparently the remove the Apple-supplied LCD and glass covering, and replace it with a new LCD panel that has a diffuser, and a black frame to provide rigidity. The fit and finish of the display model that they had at the show wasn't 100% perfect (you could tell that it was an aftermarket modification), but it was still pretty decent.
Definitely recommended if you have a 15" MBP and hate the glossiness. TechRestore can't do the 13" model yet, but I wouldn't be surprised if that shows up as a product at some point.