There's no question about the Kings taking down the few securitrons guarding the gate, but he wouldn't want to. Firstly, the King likes his position as the Top Dog of Freeside that's why he's staying. He consistently claims he's the "leader" or King of freeside and The Kings get no arguments from the Van Graffs or the Garretts. Secondly, the three branches of power under house are tribes suited up nicely, similar to The Kings of Freeside. A new addition of a tribe on the strip wouldn't fare well, leading to my next point. Lastly, The Kings forceful integration would be starting a war with Mr.House (considering this is pre courier owned Vegas, because you can RP the ending however you please) and that's starting a war they'd lose. The three tribes would have to betray house in order for there to be a fighting chance, and the Tops won't (Swanks loyalty to House is obvious, if not for loyalty his own personal gain). Mr. House brought the tribes in so they could manage and protect the strip in exchange for the life of luxury. Backtracking, if the coup d'état of Vegas were to happen from NCR, Legion, Tribes or whatever support the Kings ("The Kings" would be the least likely group to get support from groups anyways for different reasons) managed to gather how long until Vegas would end up just another shanty town?