It's possible that the mc catches troy fucking angel during the trip, but I personally don't consider that NTR, since that would be something that they already were doing before the mc ever got involved. But yeah the same way some the ntr fans will stop play until there is more ntr content, the vanilla players, and probably most of them, will stop playing once the focus goes back to the NTR route. That is why I think it would be better to have a lot of small bad endings with NTR throughout the story, that way you could offer content for both fanbases without having to focus on just one of them for long periods of time. But at the end of the day it's not my game and the dev is the one who decides how the story develops.