>... a strong political interest to not use oil anymore (as Japan as to import almost all of their primary energy), to a desire to build out with less dependence on China based minerals and supply chains ...

Given the Toyota's scale and general scarcity of rare-earth minerals, betting fully on the li-ion tech would be indeed too risky without a viable plan B towards EV. Does the world economy need any more reasons to empower China? Can't see Japan's interest in that, given the recent developments in South China sea and environs.

I hope Toyota's engineering efforts will again provide an alternative which would progress beyond the current trend.