If you own the house outright then how can the increased value force you to sell? You don't have a mortgage, and your property tax can't be that much more than a normal rent in the area. Can it?
So yeah nice on paper that the house is worth a lot more than we bought it... but that value matters if we sell and move. There is a lot more to that decision than just the property tax, however it sort of putting a time limit to it.