There has been some discussion about this lately because Musk mentioned in the past few days working on the third at latest iteration of a master plan.
That said, thinking about transportation in general, I lay out what I wish Tesla’s plan to be.
What I wish Tesla's Secret Master Plan Part Tres would be:
Build an electric jet that can rival current single passenger planes (~50 seats) with reduced crew and maintenance operating costs for flights under 300 miles. Cost savings will fuel number 2.
Note: Many electric vertical takeoff and landing aircraft are close to this (with reduced range), but my argument is to use the existing airport infrastructure and focus on longer range and higher passenger numbers instead of small use cases for alleviating traffic.
Build a network of tunnels and large electric autonomous surface passenger vehicles that augment (and eventually replace) the need for short haul flights.
Transition cargo aircraft to be fully electric and autonomous. Use this as a model for other industries (marine, rail).
Enabling technologies
Increased energy battery density
Remote pilots to act as co-pilot for passenger flights (keeping a human pilot in the cockpit)
Remote pilots act as autonomous back-ups for cargo aircraft to provide flexibility in regulation adoption
Faster boring tool creation and possibly larger boring diameters
However, Tesla will not shift to aviation any time soon, and other companies like Joby, Lilium, Eviation, the Boring Company, Boeing, Airbus and a host of others will have to fight for their own piece of this vision.
What I think the Secret Master Plan Part Tres will be
For a reduced scope of artificial intelligence (AI) tasks, implement AI in a human form robot (Optimus). This capability will improve upon and enhance Full Self Driving work to date. Use Optimus to reduce labor costs until Tesla's vehicle production goals are achieved (cars, semi truck, Cybertruck).
Build out and test general AI capabilities leveraging robot training approaches. Build capabilities into a service accessible by others.
Create a sustainable housing (HVAC included) and energy storage (battery) supply chain using recycled batteries and new mining methods.
Enabling technologies
HVAC system integrated with energy storage and management
Vehicle to X (V2X) technology on all new vehicles (X = ability to provide power to external appliances and load (V2L), other vehicles (V2V), to home (V2H) and back to the grid (V2G))
Innovative battery mining
Innovative battery recycling (company acquisitions?)
Those are my current thoughts. I’m sure Musk will swing for the fences with whatever his third master plan ends up being.