There is also the Sigma 120-300mm f/2.8 OS. Not quite as long but it's 2-stops faster at the tele end. It's heavy though, which could be a bit of an inconvenience at live events.
Heavy... yes, I have the non-OS version of this. It also has the distinction of being an internal zoom, the length doesn't change when zooming. The 100-300/4 little brother to this is known to be very sharp, is also internal zooming, but no OS.
Given the video requirements, the best thing I can suggest, is to rent the 100-400IS and try it out. Make sure that you're willing to put up with the compromises, ie push-pull zoom, somewhat spotty QA (some people swear by their 100-400, some people swear at it), older generation of IS (not tripod or panning aware).
The Canon EF70-200/2.8L IS II is an option, but it's almost twice the price once you add the 1.4x and/or 2x TC's. The IS is the latest generation, and IQ is very good, even with the 2x TC.
The Canon EF70-300L is nearly the same price as the 100-400, reviews seem to be positive so the IQ is good, it's a lot lighter and smaller, IS is the latest. You'll need a 1.4xTC to get the same range tho.
So I guess my conclusion is "rent them and try them".