This has been a big topic lately in forums, so I would do an advanced search and then when you find it (I forgot the topic title), subscribe to the discussion. The long and short of it is that people have had many different experiences at different hotels.
There is no consistency here. Some do and some don't; therefore I always call ahead of time before booking a location. Marriott should set the policy and make it consistent. All elite members and companions should continue to have complimentary breakfast.