While I have not really tested it the video chat icon does indeed show up in my Gtalk. I am running the Virtuous Unity 2.39 ROM. I am going to be trying out CM7 this week and I will see if there is any difference between the two.
Gtalk video on our phones will not work without root and a custom ROM, simple as that. If you want it you will need to root. And you can root if you have 2.3.4 pretty easily.