I normally don't recommend upgrading via wireless on Cameras however for testing purposes and to ensure that wireless upgrade path is working. I have upgraded my 933L successfully each time via wireless. I think that in most cases, wireless upgrade path will work. However, I would recommend checking for any wireless interferences before upgrading via wireless. Should there by some interferences, i.e. other wireless APs, routers or 2.4Ghz house phones that are on or near the same frequencies and channels, this could present a bad connection between the camera and the main host router and could cause some FW upgrades to go bad, thus bricking the camera. I presume that if the camera has a good stable connection to the main host router, then the wireless upgrade path can be used. However for users with physical access to the camera, I recommend using the wired path to upgrade if you feel safer using this method or question the signal environment.
My 2 cents.