I actually asked KT this on their FB page, my impression was that I was not the first to ask and that there was no plan to roll out an XD compatible version for some concrete (unshared) reason.
I'd imagine that Springfield Armory called dibs on the concept and doesn't have a product to do that, but won't let KT go ahead.
Obviously, I'd buy a sub2000 that shared magazines with about anything I shoot/carry, so XD9sc or 45c, 1911 officer, or about anything Walther ... as it is, I have a G19 compatible model and can't stand the ergonomics on Glock pistols, so I have a bin of Glock mags and just the sub2k to empty them.
Hell, I'd buy proprietary KT magazines for a 9x18 or 7.62x25 model (well, I suppose 9x18 would shoot from CZ82 magazines nicely) ... and maybe for a .45acp model ... surely for a .22lr model (we might get close to that with the RMR30)