Yes the busses run late...The Disney busses that serve The Swan and Dolphin run the route dropping people off at the other Epcot resorts also....Yacht Club, Beach Club and Boardwalk...there will be busses trust me.
I have stayed around VERY late at the park, including E-nights and MVMCP, to watch the Kiss Goodnight. I have been, what I think, the last guest out, with whatever group of people I am with, and there is ALWAYS a bus. If not specifically for the Swan, then a 'catch-all' to bring you wherever your resort (on property) happens to be.