Future Faster FDM 3D Printers - An Idea

Things seem to be progressing so fast within the 3D printing industry. I was wondering, just how fast can the FDM printers get? Are there not some sort of physical limit on speed with the current 1 extruder methods?

What are some ways to improve speed by changing the entire setup of these printers? Here is an idea.

Have Multiple extruders printing all at the same time from different sides of an object. Instead of printing on a flat hot bed, why not print in mid air (sort of). You could do this by having a "print ball", perhaps a tiny styrofoam ball which is steadily connected to the top of the printer via a metal rod. This allows you to have 3 or more extruders on different sides of the ball, all printed onto that ball at the same time. When complete the ball unscrews from the rod and will stay within the object printed. Here is a diagram. Sorry its terrible I know. Just brainstorming. Sorry if this is a terrible idea :) The red boxes represent extruders

http://i.imgur.com/Lr7rQib.jpg