The reason I stick around is to see it completed, really. I have spend so much time and it is still the first game that got me in this genre, that abandoning it right now feels like cheating. I was actually a 20$ donator in the first months.
Chapter 4 should put the focus on an end-game and for me that is a combination of D+Elena (and Jennifer). I don't want to see any other non interesting plots (such as the whole modeling part), which takes too much time and are boring AF.
In fact for the D only path (incest vanilla) we already saw an ending last year in the version before the last of Ch3 where F and D got a house, a kid, a dog and left happily for ever after.
As for the 3some or "mini harem" combinations, your favorite D+Elena (and Jennifer) is just one of the possible combinations. The most developed at this time is in fact D + Georgina. But i can see no reason to not have 2 different mini harem endings like that.
What I personally hope to see in Ch4 would be finally the long awaited full swap with Olivia and Graham which has a very good chance to become a polyamory relationship with a nice possible ending of all 4 living together, both girls pregnant, then both girls mothers, and maybe even deciding to have a kid also with respectively the other man
Additional full swinging (with R & M), maybe even regular visits to a swinger club, as well as D getting more sex with other men would be also very welcome on my side. With or without a career as a model. But (for my taste) always by agreement with F and never cheating behind his back.
D going totally slutty as a "Hotwife" (also agreed with F) would be also very nice for me but if I understand right what i red between the lines in some of the last posts, such a development (and ending) is unfortunately not intended by the dev..
As for D cheating on F and even the so called NTR in it's real meaning, which is D being "stolen" by some other man, that's something neither I nor the dev would want to see. But , well, some other guys would like that also..