If the batteries are as cheap as I think and Elon hinted at, and mining and refining and production taking advantage of $.05/w solar cells . That will drive the cost of the batteries lower without improving cell energy density. Energy density is a given with time at this point.
$0.05/W solar cells ?... Where do they come from ?
(Solar City i guess ?...and explains why they lose so much money !)
No such cell cost is available commercially.
Oh and didnt you hear?.... The solar roof on the GF has been scrubbed.!
The last time we had a significant increase in energy density, was probably 6 years ago ..when Panasonic pushed the 18650 cell capacity up to 3.4Ah from 3.1Ah (+10%)
Energy density increase has only ever been an incrimental progress, major changes of 20%+ have never been seen,...even from Tesa.
So, unless Musk is going to Pull a rabbit from his hat,...i wont be holding my breath !