I think if the show really wants us to respect it, JD and Elliot shouldn't get together. Because it's just unrealistic, especially after their history. Elliot's smart enough not to keep falling for him, and JD tends to get jealous every time things are working out great between her and another guy. And the unrequited love would be really nice, I think.

But if it haaaaas to happen, I think tvman is along the right lines.

but remember what danni (tara reid) said a couple of years ago that J.D always wants what he can't have. which is true in this case now that elliot is taken he wants her.

I don't think it will happen. I'd heard about My Cold Shower before and I was annoyed that JD was feeling that way again but once you see it you can't help but feel SO sorry for him. I think really he's just lonely and neither him or Elliot had thought about marrying before and now he's all alone. He just needs Kim back I think. I know no one likes her but you have to face it JD REALLY liked her and she's still having his baby. If she came back JD wouldn't have any problem with Elliot marrying Kieth because he'd have his own gf.
It would be good if they got together - especially since I think Elliot and Kieth don't have much chemistry at all they just make out a lot. But I really doubt Elliot would go for JD again.
But how sad was the ending when he said 'It should have been me.' And that's what he told Elliot before in season three which won her over. :-( He just wants what he can't have.

private dancer will come back, kill keith in a fit of jealousy, then JD will swoop in and save elliot, literalaly and figuratively