Apple recently filed for a US patent on "Keystroke Tactility Arrangement on a Smooth Touch Surface." The patent filing includes four different methods for achieving tactile feedback, which might be used in conjunction with their MultiTouch interface. This could make for a sweet UMPC type device.
Obviously everyone is just speculating right now, but personally, I’d love it if on-screen keyboards could provide some sort of tactile feedback. I’ve use the Virtual Laser Keyboard and as interesting as it was, I couldn’t use it daily. With no feedback from the keys it’s just too hard to keep my fingers on "home row" and not wander off onto other keys. If Apple can make the on-screen keyboard feel even vaguely like a real keyboard, I’ll be thrilled.