Nope. If you are a founder then you have bought the final game. Prior to the release of the final game you will also have access to the Alpha and Beta versions of the game.

I feel like this is not obvious at all. It needs to be CLEARLY stated on the founder description that you receive the full release game.

Also there is an Elite Founders program, which also gets you all future DLC and expansions. Good if you know you will want to play the game long term. Founders can upgrade to Elite later, but only until the Early Access deadline. You cannot purchase founders or elite founders after the game goes to Early Access, which they initially said may happen as early as late summer.

To clarify, yes you get the whole game! Purchase it now, during Early Access, or after release, you get the full game. Personally, it doesn't make much sense to charge full price and only give you alpha, or beta, or EA but not the full game at release. It's almost cruel. 

This picture excerpt may help: