Now that the deadline is set I would expect to see, in practice, all the major manufacturers will shift entirely to EV well ahead of it. They're not going to be running a factory making ICE vehicles the day before the ban goes into effect.

Now, every dollar they spend on R&D and plant for ICE is a dollar that needs a reeeeally short ROI to not be wasted. Young engineering talent will be as interested in working on them as young computer engineers are in punched cards. And if battery costs fall a little more, the cars will be outright cheaper to manufacture than ICE anyway so there is no incentive to keep building them for other markets either.

In summary, this is the final boot the industry needed, and I think ICE sales will dry up years before the actual deadline.