I don't think it will take Toyota and Honda long to get on the bandwagon. While they did take a wrong turn with hydrogen (and that's blatantly obvious in Japan where the Nissan Leaf is starting to become popular), they have invested
really heavily in electric drive train cars. It's not like they have to start from scratch.
The really big loser among the big boys in Japan is Mazda. They are reportedly just getting into hybrid vehicles in 2019 and while they are also planning a "bespoke" electric vehicle, I really don't think they are taking it seriously (could be wrong).
Mitsubishi has a production electric vehicle that I've seen from time to time in Japan. Again, the Leaf dwarfs it in terms of popularity (at least out where I live), and I'm still not sure what to make of it. I've never seen one when casually looking into a Mitsubishi showroom, and I don't think they really see it as mainstream. If you go to a Nissan showroom, though, the Leaf is front and centre.
It will be interesting to see where it goes. I personally predict that Japan, as a nation, will go electric far before the US does. The distances that people drive here are typically quite short because the speed limits are very low. A lot of people would consider 100km to be quite a long drive. I've also seen charging infrastructure pop up here (mostly in luxury hotels, but also in many businesses and apartment buildings -- alas not the one I live in).