Cosy Creator hasn't replied yet, so I am taking the liberty of telling you what I know.
The first release was about two years ago and included the first 10 days. Since then there have been 10 more releases and 16 new in-game days. I think that's pretty fast for a game of this quality.
Elsewhere, Cosy Creator has recently provided an outline of future game content. Sounds to me like material for another 2 years of updates at this rate at the very least, maybe even a lot more. Cosy Creator did not mention additional girls, and with the potential love interests we have encountered so far, it already looks like a potentially huge harem. On the other hand, there will be time skips to university, so some university students may be added. (At the very least Samantha, who already has a crush on the MC but is so far classified as a side character.)
I am not sure what you mean by limit. A limit on the harem size? Since the novel is essentially kinetic (i.e. linear), the harem has the same size in every play-through.