Let's take a look at some past themes, going back to 2018, which is the first year they started having a specific princess for each race, instead of an overall theme for the weekend.
2022: 5k Cinderella, 10k Tiana, half Mulan, challenge Moana
2021 virtual: 5k Ariel, 10k Rapunzel, half Belle, challenge Tiana
2020: 5k Moana, 10k Pocahontas, half Cinderella, challenge Sleeping Beauty's 3 fairies
2019: 5k Elena, 10k Mulan, half Aurora, challenge Jasmine
2018: 5k Rapunzel, 10k Merida, half Snow White, challenge Cinderella
So let's take a look at theming since 2018, the first year they had a different princess associated with each race. Five years, 4 races each year, that means 20 princesses used for medals. Overall totals are as follows:
Cinderella 3 (2022 5k, 2020 half, 2018 challenge)
Tiana 2 (2022 10k, 2021 challenge)
Mulan 2 (2022 half, 2019 10k)
Moana 2 (2022 challenge, 2020 5k)
Rapunzel 2 (2021 10k, 2018 5k)
Aurora 2 (2019 half, counting the 2020 3 fairies challenge as one for the Sleeping Beauty franchise)
Ariel 1 (2021 5k)
Belle 1 (2021 half)
Pocahontas 1 (2020 10k)
Elena 1 (2019 5k)
Jasmine 1 (2019 challenge)
Merida 1 (2018 10k)
Snow White 1 (2018 half)
Snow White and Merida have both only been used once, and in 2018, so we are due to have them on medals again. Jasmine, Ariel, Pocahontas and Elena have also only been used once, but Pocahontas was used most recently, and I think Elena was not a good choice to begin with, so I cannot imagine them using her again. All this to say, if Frozen is indeed the virtual series theme this summer, then my guesses for 2023 medals would be (in no particular order) Merida, Snow White, Ariel, and Jasmine.