They even pointed out how the writing in the flash forwards “sounds like it’s ripped right out of a Nancy Drew novel,” which seems to be the style of writing in the books Jughead read growing up. Even if you weren’t totally sold on Jughead dying anyway, this theory covers all of the bases in explaining away the possibility of Jughead being murdered by his best friends and girlfriend.
Who killed Jughead?
Even though Jughead might not die for real, there is still the matter of figuring out who killed him in Jughead’s mystery story about his fictional death. In the latest flash forward, FP arrested Betty, Veronica, and Archie for Jughead’s death, so it’s safe to say that, in Jughead’s imagination, they are all to blame for whatever happened to him.
Source : https://www.distractify.com/p/riverdale-jugheads-death-theory