I think we should remember that the yearly tax would be a provincial matter.
If Central Govt want to impose tax on 1600cc and above they to increase import duty but this can't be a yearly tax. There would be more mini budgets after few months (I guess)
Punjab Govt has announced that the yearly tax on 1000cc and below is to be paid once for life time of vehicle???
If any tax is imposed it would be on new cars and will be less for older cars such as 5 or 10 year old. At least this is how it should be.