Reconciliation of GR and QFT.
What do you think is the next step in reconciliation of these macro and micro laws of science? String theory and Loop Quantum Gravity are currently the most popular theories but neither make testable predictions yet. Where do you think science should focus its efforts? Many theorists feel GR incomplete. Could dark matter and dark energy be a hint to modifications to GR that leads to reconciliation with QFT? Is space-time a field that could be integrated into QFT with the yet undiscovered graviton as a force carrier? This is my favorite for no other reason than it seem to be the simplest.