I had hoped this transition for Themes and BlackBerry 7 devices would have happened sooner, but later will have to do. The official release of Theme Studio has yet to be released, but a few developers have found a work around and have themes available. Now these themes are easy to find with the new categories added to your App World.
I am not sure what countries these new categories are available in, but I know for sure they appear for United States and Canada.
If you have a BlackBerry 7 device be sure to check out the new Categories.