If Camilla does become Princess Consort, it sort of depends on how it's done. If they do an end run around the current situation where a monarch (and hence spouse) can't take other titles and announce that HM Queen Camilla will be known by the fictitious title of HRH Princess Consort, then she'll still be Queen even though she isn't called Queen, so the terms of Queen Victoria's will would be complied with. However, if legislation is passed to deprive her of the title of Queen and create her Princess Consort in her own right, or however they'd do it, that would be a different situation. Even then, what if she did show up wearing the Oriental Circlet or the George IV diadem? Apart from the tabloids having a field day, what, practically, could anybody do about it?
I believe this whole debate is really a non-issue.
Legally, Camilla became
The Princess of Wales upon her marriage to Charles.
English law provides that the wife of a noble attains the same status as her husband upon marriage, unless her status is higher than his or she marries a peer. In that case, the wife is entitled to continue to use her higher rank.
For example, in the case of a Duke's daughter, she would be styled Lady Anne. Were Lady Anne to marry a plain Mr. Smith, then she would become Lady Anne Smith after marriage, as she holds the higher rank. If she were to marry the Earl of Devon, then she would become the Countess of Devon because she married a peer, even if she outranks her husband as the daughter of a duke.
Camilla and the royal family decided to
style her the
Duchess of Cornwall because they deemed it more acceptable than calling her Princess of Wales, and use the Cornwall title to distance her from the legacy of Diana.
When Charles ascends the throne, Camilla will
legally be the
Queen Consort. What she chooses to call herself, or what the royal family ultimately decides,
will not alter her legal status. If she
styles herself as
Princess Consort, then she is not relinquishing her rights in any way whatsoever, and I expect that no matter what her
style will be, she will be crowned with Charles when the time comes.