Yeah, he was totally distressed. Or worried. Or something. Dean's still learning how to read Castiel's facial expressions. Mostly he can tell the difference between good ones and bad ones. Mostly.

"Yeah, well. It doesn't need to happen right now, does it? So it's not gonna. Look, I'll uh...I'll call him later. Let him know you're around. Let him get used to the idea. He can tell Sam, I guess. Or I will. Later."