I don't think McGregor will ever be typecast by the PT mainly cause they never appealed to the masses. A character like Archie Bunker, Tony Soprano in TV and Luke Skywalker and Dorothy from Wizard of Oz will be known by the masses cause the movies are popular. The PT are a niche fanbase of people who love them so they are the only ones who are going to think of ObiWan Kenobi when they see Ewan in some other movie.