Over a long enough timeframe, hopefully electric aircraft will become viable. IIRC it'd take at least double the typical energy density of today's lithium-ion batteries. Elon Musk does have an idea for a vertical takeoff electric jet, but I'm not sure what that would be contingent on, and certainly wouldn't be for the masses.
In the meantime, yeah, his Boring Company sounds great. Tunnels will become particularly viable for electric cars, as there wouldn't be a need for venting of exhaust gases.