In a wise marketing move, Adobe has renamed the flash player 8.5 public beta as the flash player 9 beta.
According to the Flash Player FAQ on Adobe labs, they will be publicly releasing the first beta of FP9 with Beta 3 of Flex 2. They also acknowledge that the next version of the Flash Authoring tool (code named Blaze) will target the same Flash Player 9.
Considering the new Flash Player has a entirely reworked runtime (or virtual machine, if you prefer), it would seem that the next player is taking as large a step as any release since Flash Player 5, so the full version number, as opposed to a .5 version makes complete sense.
Any of you detecting for FP8 in your applications should ensure your code is looking for a major version >= 8, not simply == 8.