Yeah, exponential growth is nice. But growth is usually not exponential - it is logistic. See Norway. Norway is the leader at EV sales with 90% of new cars being EV of some sort. A percentage that grows slowly now. Yeah, they might be ~100% EV in some years. But global average is only 16% right now, add 5 years (from now till the end of 2028) and it is likely EVs overtake ICEs. But it is next to impossible to get 0% ICE worldwide.
Out of all relevant countries/blocs only China is a little bit plausible to ban/phase out ICE entirely so fast, given their EV presence that is likely to grow further in the coming years (they would be doing the patriotic thing and kicking out foreign cars in the name of clean environment). But even that is fairly unlikely. That EU gets above 90% EVs by the end of 2028 is in my opinion unlikely too. And 90% of EV market share is still a long way from "ICE is nonexistent in new cars". And that's for EU - USA is lagging behind right now and countries like India, Russia or Brazil are even less likely to ditch ICE completely.
Of course, if you were to claim "no reasonably high volume car in 2028 is going to come only in an ICE variant", yeah, it is very reasonable that all ICE will be getting PHEV counterpart for a bit more money. It is even possible that there is no new model of ICE car developed after the deadline - with all the fresh models being only PHEV or BEV, no ICE variant. Especially as the deadlines loom.
But that there are no older models still being sold in meaningful numbers? Not a chance. Especially with many signs pointing to traditional car companies struggling with transition to EV, Tesla struggling to maintain growth and there is no chance that EU and USA simply let China flood their car market. They let that for solar cells, but too many people work for auto industry to just roll over.
About the only thing that would let your prediction come true is a massive battery breakthrough. Or, heck, a massive hydrogen storage breakthrough.
