It's come to light that the upcoming release of iOS 4.2 (due in November) will support all-out MIDI. According to Mike Keller, writing for PC World, Core MIDI on iOS 4.2 should work just as Core MIDI does on Mac OS X, meaning that your iDevice running iOS 4.2 will communicate with other MIDI compatible devices and hardware via USB (using the iPad's camera connection kit USB adapter) or WiFi, using Apple's own MIDI APIs.