For the time being. Patrons come and go.
That is, before they lose the interest over time.
As far, as I see, people who support a game are quite consistent in doing so. There was even one well known game (Milfy City) where the dev brought no update for 2 years and fell from 7.000 supporters to still over 5000 supporters. After this his fan base dropped much faster to ca. 3.500, but mostly because he couldn't deliver story-wise, what I don't see here at all.
You cannot just stay on the same level for years. You have to get better, because someone will get better.
We're still speaking about a single game. There are sure some skills and technics you can learn to get a better in story-telling and image/animation production and to raise the interactivity, but it is never said, that your fan-base would even appreciate that. It might sometimes be even deconstructive as with rising skills, you might tend to rather remake earlier parts of the game where the crowd wants consistent characters and more and faster content.
There is right now actually at least one game, I know from, where the dev starts his game from scratch in mid-production (with almost the same story), because he wants to use a new graphics engine (he actually asked if his Patrons were ok with this and the majority was ok). I personally wouldn't like that for the headmaster.
Right now, the story is well written and the graphic is decent and I got used to the whole thing. So in my opinion it is til the end of the game, more important, that the story and the character progress and the game stays consistent in itself, so the game can finally come to an satisfying end.
What comes after this is on a total different sheet of paper. This may be made with a different graphics engine and/or a different game-engine. But if the idea is good enough and the story telling is kept equally high, I guess even a game from Altosandherdone with the same engine might still be popular.
Not abandoned, but outdated. What I mean is not like books against movies, but books printed in 18th or so against modern ones. Some people indeed like old, classic stuffs, but with new technology these stuffs are made with more efficient and better quality. There are people like 2d anime, but they like it more in 4k than 800*600.
Using a new, breakthrough technology could means you have to start from scratch again. Dev may or may not want to do that, and when they do they might do it for new projects instead of porting old ones.
The game has right now ca. 3.000 patrons, which after all what I've witnessed with other popular devs right now might not go much down in the next years (unless there is some unforseeable drastic event). As far as I know the dev works as full-time-developer of this game without other main income. He makes the game right now not only to his own delight, but also to make a living from it. His posts read also rather as such of a structured man, who has an aim than that of a pure creative individualist.
When he would intend to change the graphics engine and start this game from scratch this could mean, that many of his Patrons may say: "I don't further support the game." and he would cut his own source of income.
When he would intend to start a new game with a new graphics engine without completing this one, many of his supporters may say: "I don't further support him." and he would cut his own source of income.
So I think, this two options are highly unlikely.
There are also surely still some easy accessible possibilities to raise the graphics of a game to a certain point without making it from scratch. There are remastering technics with which movies from former times are adapted to current standards without filming them from scratch, and even b/w-films are colorized. So there might be still some possibilities to raise the graphics quality if this is ever needed.