There are already Video over IP services. Many Voip carriers offer it as H.323 video protocols. I believe most of the issue is license codec and bandwidth but with open source systems such as Asterisk/TrixBox you can do Video over IP very well. The protocol is device independant so if your input supports h.323 it should scale pretty well with whatever software/pbx solution you implement. I have done very high bandwidth internal conference h.323 internally and compressed ISDN channels for satellite offices and it works great. There are software reflectors that can do it independantly but as you stated a standardized PBX solution for internal business and branch office use is probably the best route to go.
Speed bump? Hardly! The Super Ribbed of Vortex are by far the best. If you are a beginner, you need the WonderWave. The Vortex Super Ribbed is uncomfortable for beginners and you wong get as much satisfaction. Definately go for the Wonderwave.