This is a dog. Wait a couple of days.
You are right by all chances. So far, he managed to deliver update on promised date once or twice.

And yet he never failed to deliver one, despite delays, but usually, we had update, albeit week or so latter. So, no need to panic until 10th of June maybe.
BTW, RenPy is made for visual novels, and it's not easy to make sandbox game with it. Afaik, there is Water World, and Milfy City (this one more hybrid of VN and sandbox).
Why?
Is it really so difficult to write a story?
Actually, it is. Besides, he is writing in English and he is German. But, here story is not problem. Neither game focuses on storytelling exclusively.
Or hire coders to improve the game? In a month with a profit of several thousand $.
Well, it's dumb thing to play anybodies advocate here, but I will try. It won't work in way you think. First, good Python coders are not cheap. Second not many want to work with porn games, for whatever reasons. Further, his profit should be deduced first, by Patereon share, than he has to pay I taxes. Lastly, coders will do a coding, but still remain major problem, picture rendering. It takes most of time.
Anyway, guys, chill out. This is pirate site, not like we signed contract with him so he must deliver us merchandise...