I still don't think there would be a mass migration up north if there was a 10 car garage in Paleto Bay. Most players stick inside the city, I doubt they would go up north. Besides, it would be harder for them to do their *sshole routine of being a griefing d*ckhead! If a twanker comes, we can simply either take cover in certain areas of the town, or drive up to Mount Chiliad. The only way to get a tank up to the top of the mountain is via Cargobob. If they tried driving up on their sh*tty super car, they would likely drive off the side of the mountain due to their incompetent driving!
I hope they do add a 10-Car House up there eventually, I don't know if there might be vehicles with future DLC that I might want so I don't have to buy another 10-Car Garage if I brought a six car garage, or part with a vehicle I like. If we got a third property, I would be fine with a Six-Car House there.