I had a pet wolf ride in a boat with me, but when I exited, he would not leave the boat. I walked far away to see if he would "teleport", but he did not. He was standing when I entered the boat. I tried to toggle his sit/stand status, but it appeared to do nothing.

This seems to mimic the behavior of other "guest" mobs (e.g., sheep) I've had with me. If I get two in the boat before I get there, I have to kill one to get in. No amount of enticements (wheat, seeds, etc.) will get them to leave.