This is very tooooo early. We don't even know if Camilla will be Queen or remain Duchess.
Camilla can not 'remain' anything. She is HRH Princess of Wales, but when her husband is king, Kate will be DOC and eventual Princess of Wales.
The suggested title has been Princess consort, like Philip and Henrik. So instead of HRH Princess Charles, Princess of Wales, Duchess of Cornwall, she will be entitled like Philip, to use her own name. They would be HM King Charles III and HRH the Princess Camilla, Princess Conort of Great Britain.
But that would take letters issued and a new title created. In the UK, the wife of the king is queen plain and simple. I don't see her not be queen. She doesn't use POW, even though she is, because of Diana. But Diana was never queen. Its time Diana's ghost is laid to rest, and Camilla is recognized as the wife she is.
Either way, Queen or Princess Consort, she will be the senior lady at court and her tiara will reflect that. I don't think Camilla will have a new tiara like the other consorts.
-if queen, George IV or would love to see her in Queen Mary's coronation
-consort think we will see one of QEII's big guns, either the Girls or Mary's fringe (possibly the Burmese)
I don't think any of the big guns may be worn by anyone but Camilla to it.
Deli tiara may be good bet for Kate. Camilla wore it for her 1st tiara event as POW/DOC. Fitting for Kate to as well.