One of the Google Android devs stated yesterday over at XDA that those with the current 2.2 Froyo will receive the official OTA update when it is released.
Google isn't the type to release a preview to the Jurnos/reviewers/press and ditch them when the public release goes live.
Well the concern was that you wouldn't be able to update, especially if a tweaked build of FRF50 is the final update. Since Google handled the entire thing poorly (didn't acknowledge that FRF50 had made its way into non-dev/press hands, and didn't say whether it could be updated to the real OTA) people were understandably concerned about how the final OTA would work.