> proportional to their range than their size

Well and total vehicle weight impacts EV range far more than it does ICE range. So the leaf is both small and with shorter range but the gain is a smaller battery pack.

> as new battery chemistries improve energy density

You can have improved density today. You're just not going to like the charge and discharge characteristics very much. EVs have lots of multi variable problems due to their efficiency and utilization aims. To be fair it just is a harder problem to solve but the years of development and lack of clear gains are still showing obvious bottlenecks.

> so significant improvements in power to weight ratio are less likely to be forthcoming.

You can have vastly improved PWR now. Just ride a motorcycle. I think Power train Weight to Total Vehicle Weight is what you really want to think about. In either EV or ICE case there are still plenty of gains to be had here.

> Well and total vehicle weight impacts EV range far more than it does ICE range. So the leaf is both small and with shorter range but the gain is a smaller battery pack.

The Leaf isn't really that small. It's 10" shorter in length but 4" taller in height than the Tesla or BMW 3, which in terms of aerodynamics would actually make it worse (larger frontal area), but it's a few hundred pounds lighter because it has less range.

> To be fair it just is a harder problem to solve but the years of development and lack of clear gains are still showing obvious bottlenecks.

Are they? The GM EV1 from the 1990s was using lead acid batteries. A decade later hybrids were generally using NiMH. Current electric cars are generally lithium ion with double the energy density of NiMH.

Things like zinc air or lithium air batteries haven't been effectively commercialized yet but they're under development and lithium air batteries would have an energy density on par with gasoline -- without the weight of the ICE powertrain.

By contrast, what's in the pipe that is going to make the ICE powertrain weigh significantly less?

> You can have vastly improved PWR now. Just ride a motorcycle.

That's just changing the size of the vehicle. There exist electric motorcycles that do around 200 miles to a charge and weigh the same as a Harley.

But you obviously can't use a motorcycle for everything you can use a car or truck, and they're incredibly dangerous. As in, for a third of people who ride a motorcycle as their primary vehicle, that's their cause of death.