Put a run of Romex up in the ceiling with a lot of slack and directly over all the possible locations. When you know what you are doing, cut a hole for an old work electrical box, reach up and grab the romex and do your thing.
You can run a conduit with multiple T connections along the possible locations up in the ceiling, Again when you know what you want, cut an old work box size hole. reach up and fish your HDMI to the nearest T.
Of course knowing your final locations in advance would allow you to do these ceiling cuts with soundproofing in mind.