is there a rumoured release date announced yet?
how many beta weekends are we talking if you do signup for pre-order?
Theres no release date yet, people is speculating in late june/july.
Nobody knows how many beta weekends you will get if you pre purchase (note, this is not the same as pre-ordering, when you pre order you will just put down a small fee at the retail store (if any fee at all), but with pre purchase you put all your money down for the game immediately.). You will get all beta weekends that will be hosted up till the game launches, but when pre purchasing you also get 3 days head start at launch compared to 1 day head start for preorders.
So regardless of wether you are going to play the betas or not, as long as you know you will get the game no matter what, you might aswell pre purchase.