A "modest" 5-10 percent improvement like we've seen historically, for another 7-10 years, and we have more or less doubled the energy density of batteries. Plenty for EVs to beat combustion engine cars.
https://www.economist.com/blogs/graphicdetail/2017/08/daily-...
https://www.quora.com/Is-it-true-that-battery-energy-density...