I really don't think it will prompt you to upgrade, because if it did then there would be an upgrade package available for you... That's the whole point of this thread. None of us think there will be an official upgrade path from ICS leaks to ICS full. I am hoping we can leverage safestrap and re-flash /system with an old GB leak and have it patch though, but I'm not sure...
safestrap will never come in to play in getting the official update, nor will bootstrap as they don't touch some areas that the OTA update touch. Safestrap itself doesn't even allow installing .zips on the stock "unsafe" system.
You will have to hope leveraging some form of flashing a partial "current" GB version and then the OTA update taking it from there.
If the .200 to .206 techniques carries over allowing the .206 to .208 update....then it will be very likely that any official update will be achievable this way as well.
Or....Motorola/Verizon could be really nice and release fastboot files for the official version allowing all to fastboot to stock official ICS.