that since Superman has been stated to 'die soon' but with cryptic hints at it, DC has a plan. They want to see how well Jon is received as the new Superman first. If it's apparent he can stand on his own two feet as his own character, then they are going to kill off Superman and fully replace him with Jon. Not just in the Superman title but also in Action Comics.
If Jon somehow doesn't click with the fans and his title gets cancelled, they have Superman to fall back on. And then, perhaps, they will finally give what the majority of the fans have been wanting: Ten-year-old Jon.
I could be wrong but this is my own personal theory about DC's plans going forward.
Or maybe either move Superman off earth mainly now, or else jon back to legion!
Depends also what plans are for Supes in Movies, as still must be Superman for now for that!