I wonder if the Epilogue update may come with a small bit of new content besides what’s already programmed into the game — I say this because there are four* Rotom Phone cases in the game’s code that currently can’t be received:
1 and 2) the Scarlet and Violet Cases, which have actually been in the data since The Teal Mask
3) the Blueberry Case (Black), which you will be able to get from Kieran by defeating him at the clubroom after the Epilogue
4) the Neo-Kitakami Case which is a black-and-magenta themed case depicting the stylized “ogre” from the Ogerpon myth signboards
However, only the Black Blueberry Case has a method for obtaining it already programmed in. If the Epilogue update comes purely as-is, that would leave the Scarlet / Violet and Neo-Kitakami Cases unobtainable by any means, other than perhaps a wi-fi or serial code distribution. But I would think the Scarlet / Violet Cases would make sense as a final gift from Briar, who has just such a case applied to her own Rotom Phone, and who did kind of just vanish unceremoniously from the story after we obtained her book. Meanwhile, I feel like the Neo-Kitakami Case would probably be a reward for finishing the Epilogue, but at least judging from the current implementation of the Mochi Mayhem event, that isn’t so.