No. MagicBridge is made to very exact specifications for the Apple Wireless Keyboard and Magic Trackpad 2. Even a fraction of a millimeter difference in size or shape will make other devices incompatible. Belkin's Bluetooth Wireless Keypad has a round battery compartment which prevents it from snapping into the MagicBridge, so it is not compatible.
Is it compatible with a Bluetooth Wireless Keypad, such as the one made by Belkin?