According to Nikkei's unofficial sources, the Japanese company intends to invest around 80 billion yen ($704 million) in a new plant in Wakayama prefecture, Japan.
The rumored manufacturing capacity will be around 10 GWh per year. As it does not sound like a lot, considering the current stage of the industry, we guess that it's just the initial value of the first plant in Japan (equivalent to 100,000 100 kWh batteries for Tesla Model S/Model X).
Panasonic has a total manufacturing capacity of cylindrical lithium-ion cells of 50 GWh per year (including 38-39 GWh of 2170-type cells at the Tesla Giga Nevada and roughly 10 GWh of 1865-type cells in Japan).
We can only speculate that the first 10 GWh plant (if correct) would be followed by much larger sites that would supply Tesla's vehicle plants. 10 GWh is probably at least an order of magnitude too low to justify the development effort as well as the industry demand.
Anyway, it appears that things move forward and that Panasonic will launch the product in 2023, while Tesla is expected to start series production this year.
The article points out that the larger 4680-type cylindrical cells will have about five times higher capacity and about 15% higher energy density.
Combined with other improvements (structural battery pack), the new EVs might have a substantially higher range or alternatively the same range with lower cost/weight.
A simple 15% increase in battery capacity in the case of 405 miles (652 km) EPA for the Tesla Model S would be roughly 466 miles (750 km).