I'm a mechanical designer working on battery thermal management right now.
Couple comments:
Battery energy density is being actively pushed by large infusions of govt grants to get to 500wh/kg in 10 years, Tesla claims they have 350wh/kg in development, release is eminent.
In the lab, densities equivalent to diesel fuel have been achieved, but need a benevolent billionaire to go all in, or something similar, to get to market.
Battery swap technology is ready for release in the wild, it's just a matter of resolving turf wars over the business model. Everyone wants to be in charge, no one has set up a good overall standard that deals with pack aging, ownership, repeated abusers of the system (you get a fresh pack every swap, so people would be naturally disincentivized to take take care of the packs.
An Israeli company actually has/had a good system ready to go, and Tesla was on board for a while, but the drudgery of execution has taken over.
I can post supporting sources for all the above later.