Should be yes, however, according to some of the posts she isn't. Most on here want her to be but....I dunno....here's to hoping. I mean according to some of the dialogue, she seems to falling for the MC aswell. At this point I will just play it out and see where it goes.
The thing is that when you make an adult VN with family members, people are inevitably going to ship relationships with those family members so it can be hard for a dev to include this and not have them be an option for a relationship at the end. That being said, even those who aren't shipping them and who took Sumo's words as meaning that Taylor and Nikki have no chance of ending up together, have to admit that it's obvious from the dialogue, actions and expressions of these two characters that there is something deeper between them, and that they're both (Nikki mostly) too afraid to admit it.
It's this that makes it hard for some people, myself included, to believe that there's not something to this. Sure, the two of them could go their separate ways never admitting how they really feel and eventually love other people, but we like to see happy endings for the characters and that seems like such a sad ending.
Yes, almost every incest game and VN has the MC end up with one or several family members and this may seem somewhat standard, but their relationship is much deeper than the typical "fuck everything that moves" games and is much closer to a wincest type story which we don't see very often and that's why I think it needs to happen for them.