I wouldn't be surprised if what they meant is last in the "NTR series", since their NTR games that follow the same gameplay, are categoried into a "series" on their DLsite with Misaki, Kanade, Yukino, Leanna and now this being part of it.
They could also mean as in actual "no more NTR" since those are ALL selling a lot less than their RPGs, as in roughly 10-20k less copies.
If we take both highest sellers, Alcumist Colette sold 20k more than Leanna and on the lower end Hero Erina (their first game) sold 1k more than Kanade.
I just hope they won't just start to make their RPGs over and over, because they also feel VERY samey