Also, do you have any intention of releasing the HS2 character cards for the series at any point in the future?
If and when I decide that I am 100% done with the engine and series - yes.
I hope this is not the last installment!
I am sure others will ask about this sooner or later, so I'll clarify the issue straight away:
Those who look into the files of my games often find unfinished scripts I leave there by accident (or by the grace of my editor's autosave function). I have around 10-15 unfinished, abandoned/halted projects laying around. The largest related to
The Fall series has some ~6k lines written (by comparison, Valkyrie has 8k lines, Isis ~10-11k and Valdana with expansion ~18k IIRC) - and if I were to pick it up again, it'd definitely be "the" end of the series, and probably the largest installment. Alas, both my time and attention span are limited. All three
The Fall were written over the course of my holidays, and, well, I get max 2-3 of them every year. Other than that, after work I also write sometimes other side projects in Twine, though majority is not related to the genre I am most known of (the largest, is, in fact, pretty straightforward fantasy novel, just with porn) - so don't be surprised if I put out a non-corruption game out someday, it's not eating away time I spend on this series
So, is there a chance for fourth installment? Yes. It depends on many factors though, so I am not going to give you any news in that regard until I am very far into the project (I announced Valkyrie with 4/5 chapters and majority of event CG's finished) and I am certain I can deliver it. It's also possible I'll just fancy writing something else next time I get my holidays. Time will tell. I do have plenty of ideas.