If an upgrade to a meter main is required for solar, then the best option to prepare for future Powerwalls would be to ensure that the branch circuit breakers are not in the same enclosure as the service disconnect. E.g. the new equipment could be a small meter main with a main breaker and subfeed lugs, along with a feeder to another main breaker panel that houses all the branch circuit breakers. Then when Powerwalls are installed, that feeder could be intercepted and rerouted through the Backup Gateway.
Cheers, Wayne
In our area, the meter is outside the house, and the electrical panel with circuit breakers is inside the house. The electrical panels has a 200amp circuit breaker at the top that disconnects the house. I presume the meter box outside also has some sort of disconnect switch.
In my case, two powerwall would probably not be sufficient for a whole-house backup, because there is a heater with 60amp breaker and an oven with 50 amp breaker. So I would probably need to isolate them in a different panel, between the meter, and the breakers in the 60-50 amp range. So I am thinking of installing a second panel now.