From what I understood anyone who has bought the Early Bird access will also get beta. I think the email means that Early Bird will not be for sale anymore to new players after 25th August, but if you have it already, you will get beta.
Early Bird owners will be able to play the game all the way until release, no matter if its Alpha or Beta. When Alpha 3 arrives, no one will be able to purchase the Early Bird anymore until full release.
As the OP's question has been answered and in the interests of keeping the information centralised it's probably best if any further discussion is undertaken in the Announcement thread.