I work for a minor league baseball team using 3 Canon XL2s. These cameras are used primarily for tracking plays in the game and in-game entertainment. One camera is on legs at each end of the dugouts and one is wireless that wonders around the whole park. We are looking to add a static camera that will be placed in center field shooting over the shoulder of the pitcher towards home plate.

We have the standard 20x lens for all the cameras, but for this new camera, I am looking for a little more. Some thoughts that I have had is to purchase Canon's 1.6x adapter and use the 20x lens. The second idea would be to look for whole new lens entirely to handle this distance.

Any thoughts or opinions would be appreciated.

One option might be picking up Canon's EF mount converter and using one of Canon's EF lenses. Because these lenses are made for still cameras with much larger sensors, even a wide-angle EF lens will be telephoto on an XL2. This way, for a few hundred bucks you could get some extreme telephoto.

Yes, Jarrod has the right idea using the converter. The EOS converter X the lens by 7. You'll need to get a good L series lens with a 1.8 to 2.8 f-stop to cover your night games which I would think is most of your games. I would think a 135 lens would give you a beautiful shot of pitcher and batter from the center field position (400 ft away). The camera needs a heavy duty tripod to hold the camera nice and steady. You might be able to use a 85mm lens, but once you purchase the converter rent some lense's and see what works best.
You'll get great footage...I love Baseball!!