I reckon they can do it. Based on April patreon dev log, dev is writing the second half of chapter 7. There's 8 chapters total with 1 epilogue/post-game content. As long there's no sudden hiatus like a certain other fvn dev, it's possible we will get it on October at earliest.Patreon subscription is not needed for the latest build. Everyone got a perpetual Itch license for any build.
Regarding the playable chapters: Yeah, I will believe them when I got the code. No consumer can verify dev blogs or planned releases.
Side content as in all optional dates, CG etc!? We will be waiting for A WHILE. Heck they need over a year for a single chapter.
What I worried about is the art. There's a high chance that the 'final' build they release this year might not have all the CGs fully drawn yet