I'm not aware of a cap on the frame-rate polling. However polling the controller 100 times a second is pretty fast. I honestly don't think you'd notice a lag of 1/100th of a second, so really doubt that polling at say 200 times a second would really make any difference.
Interesting point @Marco80. It certainly makes a difference with mouse inputs, but a lot of "pro" mice run at over 4000 dpi and are updated at 1GHz. I guess it depends of the sensitivity of the wheel/pedals itselfYa 100 times per second sounds alot, seems odd then that wheel (and other pc hardware companies) make such a big deal and effort into getting their input rates up to 250, 500 and even 1000hz. Logitech G27 I believe is 500hz, Fanatec updated their firmware with 500hz a while ago, and I believe Thrustmaster just released a firmware update that updated it to 500 times a second aswell.
Must make a decent difference....