Dpending....It's possible they might not let you board a bus going TO MK that late. They may tell you to take the bus to DTD. Buses to DTD traditionally have run very late; until after the DTD bars close. This could, in theory, change atfer September when the bars down there close.
You don't say where you are dining. Getting a bus to MK may not be your best option anyhow. MK is kind of at the far end of the property. DTD may be a lot closer to where you are coming from. In many cases though, taking a cab is the fastest way to get back, and won't cost all that much.