Ive thought about it and heres a few reasons why the higher ups might prefer Jon:
1. Despite being written as more or less a copy of his dad, hes still enough of a blank slate that you can do what you want with him, even take him in a new direction
2. Hes not locked in to one love interest. Clark is always going to end up with Lois, but Jon doesnt have that defined love interest. Kathy was his Lana, theyre seemingly trying SuperWonder with Jon & Yara again in Future State, Bendis is having him date Saturn Girl, kid is really getting around lol.
3. Jon has an easy hook of heres Supermans kid with Lois Lane who has to live up to the legacy of his parents. Thats a quick easy to understand emotional hook. Jon can have daddy issues even if his dad is still alive, and writers love daddy issues
Jon basically lets DC reboot Superman like theyve always wanted without all the angry nerds who get mad when Clark isnt written the way they want him to be (myself included in this
). That said I still dont think Clark is getting replaced, like I said Clark is Superman in every major non comics medium, hes still Superman even in Future State. I dont see him going anywhere.