With 90% of new cars already being electric, I do not see a ban in 2025 as unrealistic. I would not be surprised if there will be exceptions (nobody sensible think that electric cars can replace ICE in absolutely all situations), but then again, with electric cars getting close 100% of new car sales by then, a ban may not be needed, as the objective of a ban has been reached by other means.
As for replacement: The average age of cars in Norway has been relatively high. We are now seeing record high sales combined with 90% electric new car sales. Getting a significant part of actual car usage moved to electrics will not really take many years.
The aim is not to have a ban, it is to change from ICE to electric. We are working on it, and it is going quite well (looking forward to getting our ID4).