He's already a better catcher than Schwaber ever was. He's not going to be a 1st baseman. I see no reason why the Cubs couldn't carry him as a primary DH and let him learn the position. But I also don't know where the deficiencies lie. He appears to have an adequate arm. I don't know about the rest of it.
Give him another season in AAA, but if he's killing the ball, don't be afraid to bring him up.