I would like a digital Canon FD mount camera with a body like the A1 or F1 rather than the T90, I liked the user experience on them. Though if I was looking for a similar user experience but had no lenses a Contax Yashica mount would be first choice. If someone was clever with the interlinking a camera could be made with exchangeable mounts.
The other one I would like to see is a larger than 645 sensored digital, somewhere around 67 or bigger. Not sure how much resolution would be ideal, it would be good to go after other IQ gains such as colour fidelity.