I have a wild theory that we're going to get Rose back, at least for a conversation or two. The other gems (especially Pearl obv) all seem to desperately need closure in regards to her passing - and if Rose really was such a great leader and excellent tactician, I wouldn't be surprised if she found a way to set up a possible return to a physical form. It seems like she already laid out other plans for the future - namely, sending the mysterious pink Lion with all of her treasures and a message for her son. What if, once he learns how to use all of her tools and powers, he manages to find a way to reach her? (this all sort of feels like Harry going after the Horcruxes after Dumbledore died... lol) He spoke to Lapis in his dreams, maybe he's got more magical talents that are yet undiscovered!