Ever since the cameo tiara was worn by three of the King's sisters - who of course were not even in the line of succession - for their weddings, it's quite clear that the cameo tiara as the Swedish royal bridal tiara can be considered a tradition. A tradition which does not necessarily have to be followed - see Princess Christina, who chose to wear the Connaught tiara - and a tradition which didn't exclude Queen Silvia to frequently wear the cameo parure on white tie occasions throughout the years.
--Previous Message-- : I have the idea the Cameo Parure is such a : major set of jewels that it is to be worn by : the (future) Queen only. Exceptions confirm : the rule but since Princess Madeleine is : clearly fading away from the main royal : stage, I can imagine she will opt for a : smaller and less eye-catching diadem. :