Likely never (if you look at Tesla's luxury vehicles almost at 400 miles of range [S and X with Raven drivetrains] and their Supercharger charge rates [0-80% SOC in ~15-20 minutes]). Battery capacity per kg and charge rates are likely to improve faster than coordinating the deployment of nationwide rail or overhead wire electrical infrastructure on interstates (a Supercharger station only takes about two weeks to install, and costs ~$150k-200k).

https://supercharge.info/map

I'm still hoping that Teslas on AP will eventually begin to coordinate and drive very close together or even attach bumper-to-bumper in order to save energy on highways due to lower air resistance. Ad hoc highway trains more or less...

For all practical purposes they have that now. The CD on tesla cars is very low, and even AP1 cars will follow other vehicles on the highway for hundreds of miles without a hitch.

The AP follow distance setting can be set from 1 to 7, and setting it to 1 just ends up with more abrupt braking when traffic encounters a slowdown. A spaced out setting of 4 is a much more comfortable setting.

If the cars were able to push and pull each other, engines/batteries could be used optimally. Cars with nearly empty batteries would recuperate and recharge if absolutely needed, cars with full batteries would pull the rest. AP would put the most suitable car in front to minimize the total air resistance... Lots of possibilities.

Might be worth designing a new type of car for this kind of use though.

Yes, but energy density is terrible. You are having to move 3x the weight not to mention the huge effincicy hit . You arent taking reality into account.

The Model 3 weighs hundreds of lb more than its equivalent in an ICE car, not 3x as much. These numbers are still improving as well.

I dont think the comparison is to ICE but to a car on a rail/line that doesnt need to carry its energy at all (or only a small battery for the last 30 miles.)

That is an unreasonable comparison to make, considering EVs are competing with ICE vehicles, not trains or busses.

But this is a tangent about rails and wires vs EV, not ICE.

It's a tangent about how to power personal vehicles, which are overwhelmingly powered by the gasoline.

Is that just path dependence, or maybe there are advantages to having lots of built in range?

The economics do not make sense. There are massive capital and operational expenditures to build power rails/overhead wires everywhere.

If you want to longbets.org this I will have someone put down $1000 this will not happen in any city of over 10k people in the United States in the next 20 years.

BMW 3 series: 3,582 to 3,764 lbs

Model 3: 3,627 to 4,072 lbs

At best the Tesla is 8% heavier (total weight).

Even buses are using batteries to move away from the trolley bus model. Maintaining those overhead lines is a pain, and they go offline all the time. I expect these will just go away outside of true rail usage.