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?