I am going to say yes, they are still a pumpkin headed person, only their head is missing. He would look like a typical man but he would be a pumpkin man's dead body. Also if the head is removable can he pick different heads? That would be cool. Final question, if we cut off his head and eat it, is it meat or even vegan? Would it be cannibalism?
It's like the headless horseman. If he was carrying his head in his hands, he's still a headless horseman, even if he has a head. In reverse, just because his pumpkin is not connected to his body any more does not mean he's no longer a pumpkin man.
That's some head dropping cliffhanger Back to the main question....is trump without his hair still trump?