I'm guessing, and this is just purely guessing, that GH will have the three go back to Llanview for some reason. I'm hoping that OLTL (and GH) decide to keep the continuity between the two shows so that it makes sense since I think many viewers will watch both shows and it'll be confusing if they don't keep the continuity (like Cole and Hope dying, Todd being found inocent of Victor's murder, Starr dating Michael, John and Natalie having a custody battle, etc). I'm hoping that OLTL doesn't decide to undo all of those storylines, and that if the three do appear on the new OLTL and come back to GH, that GH doesn't undo the storylines they had on OLTL during that time, it'd just be a big confusing mess.
I could see John maybe going back to deal with Natalie in the custody battle for son Liam. I think maybe Starr will go visit her mom. Maybe Todd will back back to try to reconnect with his kids Jack and Dani and his nephew Sam, and his sister Viki. Or, something to do with his family.