So yes I think the massive difference in running costs will drop but I suspect it won't become more expensive than ICE just more equivalent.
Sorry, I didn't phrase that very well at all. I was meaning once (virtually) all ICE vehicles are gone and EVs are all that remain.
I do agree with you that EVs will end up costing (at least) as much as petrol and diesel cars do now; it's just that (imho) they've been promoted with a twin-pronged approach of environmental benefits and big financial savings.
I don't know if either one of these factors has had more of a bearing in people buying them than the other? If people have been largely swayed to switch by the much reduced running costs (after the initial outlay), I suspect they will end up quite disappointed.
It wouldn't surprise me if we eventually see a specific tax increase based on electricity used to charge EVs - even at home - to take into account the fact that generating the electricity for them still causes a load of pollution, which they may just 'discover' in the same way that they 'discovered' that diesel cars are a lot more polluting, just as soon as they'd told everybody to go and buy one.
Once EVs are all we have, they may even just add it on as standard, so that even non-car-owning households have to pay it too - a bit like everybody currently has to pay for the BBC, even if they only ever watch commercial telly (granted, it is possible to avoid it legally by watching no live TV at all).
However much governments try to make out that 'sin taxes' are there because they want to discourage you from doing/buying something, they frequently budget and plan based on people doing just that - and worry if enough of them stop.