I still think there will be no tiara event as all, not even the reception, but can't stop myself writing predictions, just in case I'm wrong ?
The ceremony ,
Camilla: state diadem
Kate: (I guess) QMLK (I wish) Delhi Durbar
Sophie: (I guess) her wedding tiara (I wish) Persian turquoise
The reception (if with tiara), realistically thinking,
Camilla: Belgian sapphire or Greville honeycomb
Kate: QMLK
Sophie: her wedding tiara
Anne: meander tiara
Letizia: FdL
MT: Belgian scroll or emerald art deco
Charlene: ......no tiara
Mary: wedding tiara with pearl
Mette-Marit: the amethyst
Sophie: Habsburg fringe
Victoria: Baden or Connaught or Boucheron wreath
Elisabeth: her birthday tiara or Q Elisabeth's bandeau or Brabant wreath
Catharina-Amalia: the stars or the base of antique pearls or Dutch wreath
Beatrix: Emma's diamond with ruby or sapphire necklace
Other new jewelries I would like to see (especially if there's no tiara),
Camilla: QV's fringe brooch
Kate: Greville brooch
Sophie: Greville emerald necklace (the one QM wore)
Anne: George VI festoon necklace
Mary: the Connaught sapphire brooch
Mette-Marit: royal order of Victoria and Albert's badge bracelet or the diamond earrings which allegedly is QV's Turkish earrings
Victoria: Edwardian ruby tiara as necklace
Sophie: P Gina's sapphire parure
Elisabeth: the necklace gift from Belgian nobles
Catharina-Amalia: the trellis necklace
BTW in my wildest dream
Camilla: QA kokoshnik or oriental circlet
Kate: Delhi Durbar or Brazilian aquamarine
Sophie: Persian turquoise or Russian sapphire
Anne: QM's fringe or GGBI
Letizia: Ena's pearl and diamond
MT: the empire
Charlene: Charlotte's fringe
Mary: Poire pearl
Mette-Marit: Maud's diamond
Victoria: the cameo
Sophie: Bavarian pearl and diamond floral
Elisabeth: smaller setting of Spanish gift with ruby
Catharina-Amalia: shorter setting of the sapphire
Beatrix: Wurttemberg pearl with upper pearl
Sorry for the loooong post