The thing is, they already make a diesel version of the JK, they just don't sell it in North America. I think a lot of that was due to the fact that the 2.8 L VM Motori turbodiesel straight-4 engine the diesel JKs have doesn't meet US emissions standards, but they've always claimed that they wouldn't get enough sales to justify making them for the North American market. That's a pretty flimsy line if you ask me, since they're making them anyway if they would have picked a diesel engine that could be sold worldwide they wouldn't have to worry as much for this particular market.
I hope they fix that for the JL. I know I would have seriously considered getting a diesel JK if I could get one here.