Q:
Will gains in beta play be lost?
A:
Hi Kelkka.
You will retain all your characters, progress and gear when the Mac Beta period ends. in fact, there is no difference between accounts used on Macs and those used on Windows machines. As you’ve probably read by now in other posts, you can—and many players do—play on both types of computers.
The client is beta, the game is not. Everything that you do/acquire will not go away should the client go live or go away. It’s stored server side.