In September 15th the gates for players open. But only if you buy Epic or Legendary Founders pack. Is it worth it? If you like the game then probably it is. Because then you will be able to play 1 month starting in September and then 1 month starting in December. Then there is going to be Closed beta at the beginning of 2015 which will last until open beta which is in reality launch.
So now it is up to you but it seems that there is not going to be any similar games in the future so it can be nice opportunity to start something different with sandbox feeling.