How it could end for the Robins
I have a theory on the fates of the Absolute Robins.
Starting off and oddly with Jason Todd, simply put he dies and he doesn't come back since in this universe there is no Talia or Lazarus pit to bring him back. But I feel like he's death will have an impact on the whole Robin team. Jason's death may cause some infighting which ultimately leads to people going their separate ways. For he's cause of death, I would say Joker. I think Jason will be the Robin to realize that the Jack Grimm is not who he says he is but due to the Joker's influence Batman will be blamed for killing a Robin, which leads to the public hating him.
Secondly, Stephanie Brown. She will become Spoiler in an attempt to stop Jack Grimm, dig deeper into what exactly caused Jason's death and expose Jack Grimm. Her and Jason will have a conversation before his death where he reveals to her why Jack might not be what he appears to be. Initially she might think he's crazy and ignores but as she puts pieces together she realizes maybe Jason was on to something.
Thirdly, Duke Thomas. He will stick with the Joker and become The Signal. Now he's a bit tricky but I think considering the possibility that Joker doesn't truly care for the Robins, Joker could have the doctors from Ark-M experiment on him and give him his metahuman powers. Joker may sell the idea of getting stronger and "not letting what happened to Jason happen to an innocent person " to Duke which leads to him agreeing to be experimented on.
Fourthly, Tim Drake. He will stick Joker but compared to the other he might get closer to him and become the only Robin maybe rebrand to Red Robin. Now this leads to Tim being darker.
Finally, Dick Grayson. He's tricky honestly because in the mainline universe he got the idea of Nightwing from Superman. So going with something completely different... Absolute Red X 😅 (which admittedly I don't like the idea of that). But if I had to really try, maybe Slade may have a similar story which leads to Dick Grayson becoming Nightwing. He may choose to become Nightwing because he wants independence, he's outgrown the Robin mantle and also due to the death of Jason he may feel like he's not fit to lead a team and hates Batman even more.