With robotic walkers like Asimo and more curren variants, the prospect of a real Mech isn't terribly far fetched. Realistically, the last major hurdles are power supply and pilot interface.
-Power supply need to be safe, portable, and last longer than it takes to charge
-Interface needs to either run static models to make generalized movement, or iterface with the pilot in such a way that he can conrtol everything, just as he controls himself.
This is an example of the hurdle:
http://www.geekologie.com/2007/03/walking-robot.jpg
No running, no stairs, just "mosey". if you can capitalize on the pilots own sense of balance and he exsisting reflex control, you can have a much more agile and versitile device.