I have heard froms omeone that some blue poster said, that only accoutns with payed wow and sc2 will be choosen for closed beta! is that true?

i hope he was trolling, if not, there would be some million of ppl pissed at you :S

This was bad information. They confused requirements to post in the forums to requirements to be able to opt-in. They're not the same.

To opt-in you need to create a Battle.net account and attach any Blizzard title that has a CD-Key you can attach. If you're opted in then that means you do have a game attached, and you're all set - you're in the pool to be selected just like everyone else.