A few things:
1. I'd move him as soon as you can. We moved my daughter out of the nursery about two or three months before the baby came. That way, it was all about her getting a new room--not about the baby taking her old room. By the time the baby came, the new room was old news, and she didn't associate the two.
2. Are you planning on switching him to a big-boy bed in the new room? That might be too much at once (new room, new bed, new baby)--unless, of course, he shows excitement about it. I'd do like you suggested and move the crib into the new room and wait for his cues as to when he's excited about trying the big-boy bed out.
Good luck! My oldest was 20 months when our younger daughter was born, and she adjusted to the new room and the new sibling beautifully. I wish the same for you!