It's implied that he likes her. In chapter 55 he asks Machi to stay with him for the night. However, he seems to be attracted to most strong people.
I agree. I guess Hisoka has some interest on Machi but always ended up being rejected. I know he's hurt when Machi said that he can die after the job for all she care. That's why he asked her that kind of question about what she will do if he kills Chrollo. I mean, Togashi must have some kind of reasons for putting that kind of dialogue between them, right?