Yup, the 1st line of my post: This is a OS testing program, MS account and HWID will be recorded in MS activation servers under the generic key, so if you opt out of MS account, MS won't be able to match the OS with records in activation server, and the OS will be deactivated. I don't know what would happen(at least ATM) if people tried to disable Windows Update so that the RTM won't be updated to the next Preview release, my guess is Windows Service will notice that it's a Insider's RTM build, and after a pre-set "reasonable time", it will send out a reminder/warning that you need to check WU, otherwise....(I don't know).
Why are we all excited about an OS that is half baked feature set wise and will be full of bugs? I mean the OS as a whole isn't even finished as we're gonna have rolling build updates. Those updates are ridiculous to install as well because they are something on the order of 2-4 GB to download.
Win7 is only finished because they went on to Win10. I think 10 is just a far more obvious lesson in OS development than previous. They have all been a work in progress, this just screams it loud and clear. Nothing different since Win98/5
They don't have to upload to everyone on the same day. The GWX config file indicates behavior for RTM and for GA. It could possibly download an encrypted ESD after RTM and only get the decryption key at GA.