The problem is that it puts a hard cap on how many people can enjoy your home theater, so that might be an issue. If you already have a space carved out for a home theater and were thinking of entertaining >2 people then I'm not entirely sure what the value add of the headset would be. In my opinion the benefit comes in getting a home-theater-like experience that you can bring anywhere and not have to dedicate space in your home for.

Third party developers will definitely be capable of adding a sync feature like you're describing but I have no clue if they will.