I've only had one other early acess game on steam, but my understanding is no. You buy it, you get all versions all the way to the end. In order to charge more, they need to release a version 2 or DLC
I've played a few Early Access games and I've NEVER had to pay more once the game was released. That would be an extremely bad move for any company to make.
No need to pay twice. You paid for gold and were just given early access on top of that.