Wheelbase is only one part of the equation. In addition to the top tube length and the steering tube angle, you have fork rake and trail, chain stay length and seat tube angle to consider.

And yes a short wheel base bicycle will usually turn in a shorter distance than a long wheel base.

For extremes take a look at a Raleigh Tourist rod braked roaster or a Surly Big Dummy for the long wheel base and slack angles. Look at track frames for the shortest wheel bases around. One bad thing about moving stems around is that it can affect the center of gravity and change the handling drastically.

Aaron