14.99 USD isn't the final price for the game since it'll definitely be raised when the game is complete, but purchases are one-and-done. If you buy OBSCURA now you'll get the rest of the Chapter Two and all of Chapter Three as they come out, same if you buy it later, the price may just be a little higher. If you use Steam or Itch.io's app (and we are including Steam keys here on Itch.io now) you'll get the new chapters automatically as updates, otherwise you'll get an announcement about the update and just need to download the updated build.