Areas for you to consider:
Hydrogeology- the world will need more water, and understanding how water moves through the rocks underground will help us to pump it out efficiently and better understand how aquifers recharge.
Petroleum geology- despite conventional wisdom, we are going to be using oil and gas for a long time.
Mining geology- with more focus on renewable technology, we have to find more rare earth metals.
Environmental geology- regulatory requirements will force companies to maintain more geologists who understand how the environment is changed by industry.
Petroleum geology and environmental geology will be the two fields that are going to endure into the future.