Like everything the first few hundred thousand are going to cost a lot more than the millions that follow. And like everything else, it won't happen all at once but one segment at a time. Probably starting with the companies that own a fleet of local delivery trucks.
I am not an engineer by any means but the wheel motors I have seen that capture the regenerative braking are tiny, while these would have to be upsized in a truck I don't think they would be any heavier than existing truck brakes.
And I totally disagree that diesel will only be around for decades, it will be around around a lot longer, in my opinion. The amount of concentrated energy in those dead dinosaurs is going to be hard( maybe impossible) to replace, at least until we have flux capacitors

I think there will always be applications where it is the best and possibly only workable solution.
In my own industry, commercial fishing, while day boats could and will eventually become EVs or possibly hybrid, I can't imagine it being possible for the boats out fishing for weeks/months on end, power needed is just too large and the consequences of losing power are really too large!