Theon has had one of the longest journeys in the Game of Thrones universe, and he once even killed people at Winterfell in front of Bran.
Those two characters clearly have history together and there needs to be some sort of resolution between them at some point.
Isaac Hempstead Wright has previously discussed the scene in which Theon killed Ser Rodrick Cassel in front of Bran was incredibly difficult to shoot.
Like with Jaime, I would assume Bran has some thoughts about Theon, and his homecoming to Winterfell would have implications of a different sort than bringing in the Lannister with the missing hand.