I've thought of it many times, actually an "ally" due to the petro dollar, what programs has Saudi Arabia implemented to prepare for a transition to a post-oil world economy?
The crown prince has laid out a variety of diversification measures in something called Vision 2030
Major parts of this include:
Selling off 5% of ARAMCO to be traded publicly (the state's national oil company, often cited as the most valuable company in the world) in part to create a massive sovereign wealth fund.
Creating a megacity in the middle of the desert to be designated as a special economic zone for economic cooperation with Jordan and Egypt
Socially modernizing the country (to an extent) and starting a green card system to attract foreign investment and foreign peoples who otherwise might have avoided the historically ultra socially conservative state.