Stewi - before we go multi-gantry or multi-head, we need to nail down the closed loop positioning. This is something that is totally lacking in sub-$100k machines and can greatly improve reliability and pave the road to higher speeds.
There is one great thing about KFLOP motion controller - it can take up to eight encoders and close the positioning loop properly.
After that I would really like to see linear motors on X and Y axes. They will greatly simplify mechanical design and make machine lighter and more compact and reliable.