Maybe I am miss understanding something but the patreon members who have paid get access to all versions as part of there deal when a new version is released and as patreon is a monthly payment that is hear nor there. (they know they will be paying monthly)
But asking people who are not members of patreon to pay before they can play it seems fine to me. I have bought some games on this site before and only had to pay once to get access to the current and all versions after that without paying any more. I am assuming that would be the same for this game on this site, pay "once" and you get access to your goods and all content there after.
Now if the next versions just contain the next part of the game then sure no extra charge however if he is releasing 2 versions 1 with bonus content similar to DLC then asking for an extra $3 or $4 for that content then its understandable, many company's ask for money for dlc/bonus. As long as the version you are getting has bonus then asking for some money is ok however it should NOT be full price.