If I was going to buy a new car, I think I'd probably only consider a sub-130g petrol or a hybrid, anything else is just asking to be caned on tax. They are going to have to pay the Brexit costs somehow, and slamming polluting vehicles is an easy target.
As it is, I think I'll just keep my Euro-6 diesel for another 5 or so years and throw it away when it becomes worthless, by which time hopefully we'll have decent range and charging infrastructure on pure EVs.