Idle speculation but I'll spoiler tag it anyway. Chapter 5 is coming out soon
Looks like it will be Yuna's chapter so will likely get a Yuna SR from doing it. All the other story SR's have an SSR variant so wouldn't be surprised if we get Yuna SSR on the banner too. People are also speculating that the next tales SSR could be Sophie from Graces due to her being in the DAT mines.