I'm a fan of Ehrman. A lot of people can't stand his raspy voice in debates, but having a signature voice is what makes a debater/philosopher/etc. great. (Of course there's nothing wrong with a raspy voice, it makes you tough ) My thoughts on what he said in the interview, I definitely can understand what he's saying. It's a plausible explanation for sure. A Christian response, indicating a bias, would be there's not necessarily a progression seen in how early Christians viewed Jesus within the Gospels (for instance Ehrman saying Mark doesn't necessarily say Jesus is God to the Gospel of John saying Jesus is God), but the Gospels themselves wanted to emphasize certain points about Jesus. This could be plausible because it's certainly true the four Gosepls were speaking to different audiences. Ultimately I understand what Ehrman is saying. He's not questioning whether Jesus rose again or is God, but he asking the question if Jesus Himself ever said He was God while He was living. If that was always the understanding, or was this an evolution of thought.
I will argue, and perhaps I'm bias, the OT surely predicts this kind of a situation. If we are talking the doctrine of the Trinity, there were plenty of instances where it seems like God was made up of distinct individuals. The reference of "creating man in Our image" back in Genesis, the Angel of God referring to himself as God at times (This can be seen when Abraham was stopped from sacrificing Isaac and other occasions), the act of Samson's parents saying they seen God in the man who talked to them about Samson. So there is grounds for the Trinity doctrine in Judaism. There's also plenty of mentions in the OT, that would be best explained by the things said of Jesus. It's certainly possible Jesus picked up on things written in the OT, and declared Himself to be God historically.