No, it's not possible to upgrade to a "higher non-beta" ( Wouldn't life be wonderful if you could.)
My advice is to stick with your current version (whatever that is?), as the beta still has some issues.

The beta works but it's not bullet proof just yet.

However, beta feedback is important so if your into contribution, do it. If your a careful type then just sit it out until the final release arrives

When will be the final realease?

The date has not been announced. Keep watching www.b2evolution.net for the announcement.

Personally, I hope the developers take their time.