With the electronics available today (e.g. single board computers smaller than the palm of your hand with built-in pwm servo control function for less than 10 bucks), It would be easy to add relative wind sensing and command a sheating servo in response... or to sense and correct direction... actually, it would be pretty easy to have the computer use those functions along with the location of the next waypoint it's headed for to [somewhat] optimize its route to the point -- and, while we're adding to the function, you could add an override in case it experiences a local wind that has it sailing into a calm or otherwise unsuitable area.
It would be a lot of fun to build, but not a lot of fun to "sail"