2019 will see the start of Beta phase and the final release of the game. However if you buy an Early Access release like this one, or the Steam one, each update of the game will be free for you forever, including Betas and Alphas :)
Only Patreon pledgers have an earlier access as well, with a free Steam key if they reach 30$ in pledges overall, plus more rewards, but that's a different thing.