New member here. Couldn't lurk any longer and had to join the conversation. I have some insight in this topic; working as a developer for official M$ partner, living and working in Redmond area, friends on Windows 7 team etc...
Anyway, I have to agree with Traxan. Release in RTM means release from dev group (sign off from dev, test) to manufacturing. After RTM, any new build will be for new release (new hotfix, SP, full release). The identical bits from RTM will be on the shelf come October whatever. At the same time, M$ can distribute that same release to testers, OEM partners and whomever they see fit. As a MSDN subscriber, I remember seeing Vista RTM build some 3-4 months before it was released to the public (read -store shelf). Software partners and manufacturers like Dell, HP and so on need enough time to roll out their products with Win 7 or working on Win 7. We as a company have started testing and adopting or product for Win 7 since pre-Beta, and I'm expecting to see RTM build on MSDN subscription site shortly.
Also, friend from Win 7 team said that most Windows 7 feature teams have RTM-ed internally and are working on future releases for some weeks now. So I believe we are close to seeing RTM build in public. Long winded for the first post, so excuse me if I bored anyone to death.