I believe it supports them, just like it supports game controllers now, but apps will have to include their own implementation of support to actually make use of them. It doesn't seem that iOS 7 supports using a mouse/touchpad by default throughout the OS itself.
Looks like apps can only support arbitrary Bluetooth devices if they're the Bluetooth Low Energy type: http://stackoverflow.com/a/11892685. Conventional Bluetooth devices would have to go through the MFi program to be supported by App Store apps.
