Don't know about the "final" release (?), but the first
public release of OS X is supposed to happen around
March, 2001.

Given Apple's notorious history for late OS releases,
and the fact that this is an all-new bet-the-farm-on-
the-release OS, I'll bet late summer 2001 at the
earliest, Christmas time being conservative.

So let's say 1 year from now.
the current public beta expires on May 15, so I'd expect it to be out by then - there really isn't *that* much Apple has to do; most of it's in the hands of application developers now.