Will the beta(s) be upgradeable?
I'm sure the official answer will be no, as it always was for the Test Releases in the past.
In practice, maybe, but the results aren't guaranteed.
If you have an existing pclos keep that as your main system. Install betas as a test in a spare partition if you have one.
The only people who might, with some justification, be tempted to use a beta for a main install are new users who can't wait for final and are prepared to take the risk on themselves. Even then they probably won't get any official support.