Re-examining rates of lithium-ion battery tech improvement and cost decline

Fig. 8 shows the 2019 energy density is around 725-750 Wh/liter, which is similar to 2013.

At the risk of conflating Wh/l and Wh/kg, the 85 kWh Tesla Model S from 2013 weighed about 4600 lbs, while the 100 kWh 2021 model weighs a proportionate (yet still porky) 4900 lbs.

I do understand the modern 80 kWh Model 3 weighs a relatively svelte 4100 lbs. When should we expect a 3500 lb version?