I emailed springfeild armory awhile back asking why didn't they make a XD in .45 and I got a reply saying that there researce and development team was working on it and that it should be out soon but thats all they told me
The XD was originally chambered in 9mm, and the frame was beefy enough to stand up to 40 S&W (Eastern European ammo is loaded a lot hotter than US SAMMI spec). The pistol was originally named something different and only had moderate sucess in the US, but Springfield bought the Croation company making the pistol (so I have been told) and renamed the pistol. The reason for the delay in a 45 pistol is probably the cartridge is a lot bigger than the 9mm/40S&W, so some parts will need to be scaled up and retested.
There is a member of the HS 2000 forum(what now an XD is named)Who lives in Croatia. About 3 weeks ago he had a post where he went in the XD factory on a tour. He was told they can't produce enough XD's at this time to offer many more models. Some folks want the Compact XD in a .40, but is only available in a 9mm now, and alot of folks want it in a .45. By the way the barrels are produced by the same company that supplies Walther their barrels.