I love how there's apparently no possible scenario where Anna would join the DP franchise by herself.

I don't think Frozen will ever go down in popularity enough that the sisters would be "demoted" to official DPs.

Probably. Otherwise some other heroines would have already joined as well.

It'd be really unfair if only Elsa joined, since she isn't even the main character (or at least so I see it; and unlike with Jasmine and Aladdin, Frozen's protagonist is a princess). If anything, only Anna should join imo.

I'm not the biggest fan of either anyway.

Only Elsa is liked in my country.

Both can sustain their own franchise unlike a certain fish.

It seems like Disney did everything they could to keep them from joining the princess lineup. They made Elsa queen and then used the popularity as a reason to keep Anna from joining the lineup. Now Anna is queen, so she can't be in the princess lineup and Elsa is being promoted as the 5th Spirit (not as a princess now).

Honestly, I would hope they join the lineup like Moana did after some years, but I am not sure they would do that.

For obvious reasons. Frozen was for the part of the Disney fandom that got sick of the Princesses, and sought to ridicule them. Doing that, split the fandom between two opposing sides. I don't see the reason to join the Frozen sisters with the DPs. I didn't see the reason in the first movie, and I sure don't see it in the second movie.

TLM franchise is doing just fine as a stand-alone franchise, thank you. Ariel got an exclusive Hallmark 2019 30 Years of The Little Mermaid limited edition ornament last year. Ariel has a lot of items in the Jim Shore Collection, and there's a lot of giclee art of Ariel on the Disney.com website. The Little Mermaid got an exclusive promotional interview and Q&A last year on GalaxyCon. Slots for the interview SOLD OUT IMMEDIATELY. No need, Jadis, to be cruel. Ariel is still very popular, and she has plenty of fans.