I know it is heretical to say on this board, but I do believe that when Windows 7 hits the shelves that the build string will be 7600.16399.090722-1835 or higher. Most users are using leaked builds still and don't know where Microsoft is in their process. The OS may be finished, but there will likely be last minute "fixes" integrated into it.
OEM's might get updates slipstreamed in themselves, but it's highly doubtful MS is going to issue them new confusing OEM builds.
RTM is RTM. It's off to manufacturing. It's what shows up on shelves. And unless something is full-blown unpatchable or a total disaster, it's not recalled.
They have only two months until they need to start shipping things overseas, etc. They can't start re-manufacturing things every week.
You might see that build string show up on things OEM's customize, but it's highly doubtful it's what shows up on the shelf in the standard retail box.
When things get released to Technet/MSDN Thursday, it should be clearer what's occurring. If they're 16385 and updates show up on Windows Update in a week or two, well, that's probably what it's going to be for consumers, too. The kinds of IT people who subscribe to those things need to start thinking in detail of what happens if they implement something in the workplace, right down to patches to install on day one.
Anyway, RTM means stuff is actually released to manufacturing. Yes, they're going to keep making patches, hotfixes, etc., for Windows Update, but it's not practical for them to integrate things "last minute" at this stage. They have millions of discs and packages to print and ship, and it's not exactly a one day task.