Why not? Every game is televised and with multiple cameras. We get replays on our screens within seconds of the action occuring - Henry's handball was replayed even before Ireland had kicked-off. Surely a radio link between the video ref and the pitch ref wouldn't be impossible to setup?You really can't trial something at the World Cup Finals!
Especially when anyone that has actually thought it through realises that it would be a shambles and open to some serious abuse.
As far as I can see, the only people that have 'thought it through' are those who demand it for all matches. I don't see too many people arguing that the technology itself is bad - unless you count the purists who are against any form of change.