Hi Dantheman.
The bearing would work well too, but the reason I was thinking magnetic field, was because I recalled this short vid with George Green.
http://www.projectcamelot.org/magnetic_motor.html
If this type of motor was constructed "around" the central shaft, it would serve the triple purpose of reducing friction beyond what a bearing could manage, plus add it's own "push" to the shaft's rotation. The turbine could conceivably be always running, wind or not.
either system on it's own would be less than the complementary whole of using the magnetic motor to both add rotation and isolate moving parts from friction.
The magnetic motor might not generate much juice on it's own, and the sail would be still when there was no wind. But together....