Q u o t e: I highly doubt Diablo3 will have any sort of open or closed BETA to the public...
Im sure it will be in-company testing until release
That doesn't make much sense considering there is a beta opt-in option on battle.net for "Diablo universe". And lets not forget that Blizzard had public tests for WoW, WoW expansions, and SC2. The logical answer would be to suggest that there would be a public beta for Diablo 3.
"Go then, there are other worlds than these."