We can agree that the promotion is most likely going to work this way, and that the mount will come form it, but Blizz has yet to confirm it. Plans change sometimes.
What's more important, and interesting, is IF this is all true, then you can bet your ass that there's going to be an open beta at some point. Blizz wouldn't limit this mount to people who got lucky enough to win entry into the beta.
One of the developers said that the great thing about Hearthstone as a new game, was that once the beta had been going on for long enough and they had all the data they needed, they could just hit the "reset" button and call the game released since everyone was already playing and on the servers.
So by that yes there should absolutely be an open beta at some point before they hit the "reset" button, i can't see why they wouldn't really. If their server can't handle the pressure before the launch why would it be able to after the launch? (and yes i said server, as in a single server, maybe one for each language at max, it's a 2d game after all) most of beta should be about game balance not fixing bugs, glitches etc, and the more data you have for balance the better off you are.
In alpha right now it seems like they are just focusing on the really obvious imbalance, like the latest +5 health to the person going second and such, or changing cards dramatically like we saw in the live-stream to some cards.
I think the thanks for beta testing the payment system will be Hearthstone related (E.g. Achievement, Special Sleeves, Alternate Art or maybe a unique emote) as the Beta testers may have never played WoW.
You have the same CPU, memory and nearly same gfx card as me :O
OT - I hope so, I am at the same stage!
Can i still do something to get into the beta? i love that mount and would like to try out Hearthstone aswell!