Regardless, let me add another wrinkle: since we are all speculating here, how about a 400-mile range vehicle, say, 110kwh battery or so for the Model 3? Achieving a 300-mile range is huge, and pushed me to get the Tesla. Even though I no longer have a commute, I very much appreciate the range on trips, and it makes Tesla a vehicle that can mostly replace an ICEV with the exception of built-in towing ability, at least factory-optional on many 4-door sedans. With Rivian’s longer range, the upcoming Roadster’s range double that of the LR RWD, the 500-mile Semi, and other brands edging to 300 miles, I think my next vehicle’s range will far exceed that of any ICE today.
IMHO, there's a point of diminishing return on range increases, and it's somewhere in the 200-300 mile area (probably closer to 300 miles than 200). This is especially true with faster DC fast charging; with Tesla's announced 250kW Superchargers, it's possible to add 200 miles of range in a ridiculously short period of time, which means that you won't be slowed down on road trips, even in an SR Model 3. On my last long road trip in a plug-in hybrid (from Rhode Island to Cincinnati and back again, using the gas engine most of the way), I took notes on how long I spent driving vs. stopped, and it turned out to be about what I expected: For every ten hours on the road, with wheels turning, I spent two hours stopped -- mostly using the bathroom and eating. At that rate, even a 120kW SuperCharger and SR Model 3 would be plenty to not slow me down.
There is a caveat, though: EVs suffer from range losses and, frequently, degraded charging speed, in cold or very hot weather. Other real-world problems, like a SuperCharger site with 100% stall occupancy, can cause delays. Factoring in such problems, you'd need faster SuperChargers and/or longer range than an SR Model 3 to keep up with my personal road trip driving habits. Of course, not everybody likes to drive in the same way on road trips, either. If you're the type who likes to drive for five hours, stop to go to the bathroom, and hit the road again with a burger in your hand, then bigger batteries and/or faster SuperCharging will be desirable. I suspect that this type of usage is on the extreme end, though.
I suppose another use case for EVs with longer ranges is people who can't charge every day, such as apartment dwellers. As EVs become more common, though, I expect public charging infrastructure to improve, so I'm not sure that these people will really need cars with ranges of over 300 miles, at least not in the long term.
Adding bigger batteries has at least two significant downsides, too: They add weight (therefore reducing efficiency) and they add cost (both in terms of money and in terms of environmental problems associated with battery production). Today's EVs aren't much less expensive to buy than were the ~100-mile compliance cars of a few years ago, in large part because the dropping price of batteries has been compensated for by putting larger batteries in the cars. If manufacturers stick to 200-300-mile EVs for the next few years, then they'll be able to reduce prices, thus enabling the vehicles to compete with otherwise similar ICE cars on price, even after government incentives end. Personally, I'd rather see that happen, along with improvements in DC fast charging infrastructure, than see 400- or 500-mile EVs.