Yeah, a Nema 17 motor can push a larger bed than the Taz has around without risk of failure. You could step up to a wider belt and or a NEMA 34 motor if you wanted to, though you would need to figure out what if anything you would need to do to adapt a NEMA 34 motor to work with a Rambo board, etc. You could go leadscrew, but the speed just isn’t there at that point.
NEMA17 motors should be fine. Belt stretch will be a problem long before the motors will be.
However, it depends on the bed weight, and quality desired. Cutting solder paste stencils on a Taz with a ~10lb aluminum plate bed, I could see ~2mil (50 micron) protrusions at the corners of square cuts at ~20mm/s travel speeds.
Personally, using dual threaded rod drive for my Taz_Mega Y-axis. However, this is expensive, and as piercet pointed out, speed is more limited, to ~100mm/s travel speed.
EDIT: If the stepper motor gets too warm, an easy fix is to apply one of these heatsinks with thermal epoxy.
http://www.amazon.com/dp/B006Z4J8JE/?tag=hacdc-20
http://www.amazon.com/dp/B0087X725S/?tag=hacdc-20