Given that room-scale VR drastically reduces the prevalence of motion sickness, I’m assuming that sensory conflict (vision not matching up with inner ear) is the more serious blocker compared to vergence-accommodation conflict (eye lens not matching up with eyeball orientation).
The most promising technology I’ve seen that addresses sensory conflict is Galvanic Vestibular Simulation (GVS), which is the process of sending electric messages to the nerve in the inner ear that maintains balance. The ultimate goal is to trick your inner ear into sensing the movement that your eyes are seeing on the screen. I mentioned a while ago that the startup vMocion had licensed the Mayo Clinic’s GVS research with the intent of applying it to Virtual Reality. However, no new updates have shown up since last year, so I don’t know what if anything will come from that venture.