I doubt it.
The sub route is my main, but also playing the neutral, path. I caught the hints early that maybe Lisa was "different", and among other possibilities, I thought, "Please don't be a futa!" Never saw conclusive visual evidence.
So, I can't say I know for sure if she's a "normal" woman. I really hope so, because ED is beautifully written. Introducing bizarre twists is something that trashy porn games do. Such a fate is totally unworthy of the mesmerizing ED.
I dislike futanari in general to be honest. I specially would dislike this game to have it, as so far for me this game is about strong almost perfect women that are real complex monsters inside, which I find amazing as plot driver.
However, I am almost sure that I remember reading Dev said he was planning to include something like that. Still, making Lisa futa would feel too much to Starless, where oldest daughter is one.
Regarding the scene where she masturbates, she clearly does not look to me to be a futa the way the scene plays, but who knows... anything can happen with enough imagination.
I strongly hope there is no futa content included at all, but whatever happens the quality of this game is amazing, so hopefully even if it happens is still tolerable (after too many years reading erotic visual novels I know I won't like it no matter what)
Disclaimer: I am not trying to be a douchebag even if I sound like one in this topic, I can't help what I like or don't. Still, I am sorry if somebody felt offended (these days it always happens), it was never my intention.