The land itself isn't going anywhere. The sands of Saudi Arabia won't sink below the sea. The physical country will still exist. But what kind of government, what kind of state, can afford to govern that space and provide for its people, without oil revenue?

From certain perspectives it hasn't been that great of a state even with massive oil incomes. It will probably continue to be a state with massive wealth inequality and repressive government theocracy. It'll just have more social unrest to possibly change the status quo. Maybe people will really start to demand change there.

It will be like any other country in the world. We should hardly feel sorry that they’ll no longer be ridiculously pampered and looked after by an underclass of mistreated immigrants. They have enormous opportunities, both in other available resources and in a capital overhang, to make their way.

Indeed. Can you imagine the alternate reality if the Saudi branch of Islam was something more like Sufism instead of Wahhabism, given the number of mosques the Saudis have funded all around the world with petrodollars?

Violence and instability in the middle east has caused problems in western countries. Of particular note are 9/11 and Europe's refugee crisis.