The CPS have six months from the date of the alleged offence to bring the matter to court. So unless that period has elapsed there is still a possibility that you may be charged.
The saving grace is that, had you been sentenced for both at the same time you would have received a fine for the careless driving but no penalty points or additional disqualification would have been imposed. This principle should hold good if you are charged separately with the careless driving but you must bring this to the court's attention if the prosecutor does not.