So you guys wanna see something kind of funny? Seems like in a recent interview Bendis kind of let slip the whole plan for Jon and basically no one noticed. Even funnier, it was a Legion of Superheroes interview from this very site.
https://www.cbr.com/interview-brian-...es-millennium/
"I got to tell you, I'm very proud; I actually first got to pitch this to [DC Comics Co-Publisher, Dan Didio] the first time we met each other just to see if we were going to do this. He was talking about something that he wanted and I mentioned, "I don't even know if the pieces line up with this, this, and this but if it's [Jon Kent] who gets to go, you still get your Superman book but you have Superboy teed up for a completely original journey as a hero that's different than his father's and then they have to deal with it as father and son too." That's unique and everyone got real excited about it."
You noticed he said
"you still get your Superman."? Over the past few months I've become more and more sure that Jon getting aged up was always going to happen because 5G and seems to have been in the works long before Bendis, but it actually seems like Bendis was the one who sort of finessed this into a Superboy and the Legion story. I think early on before Bendis the plan was likely to have Jon age to adulthood with no in between, and Bendis said something to the tune of "can I have an extend period with teen Jon before that for the Legion?"
It also seems like he's trying to do an "Ultimate" take on the 5 Years Later version of the Legion by using Jon having to age to young adulthood. He's been calling all of the Legion members "freshmen" as a way to continue the overt college metaphor he has for the take, so 4 or 5 years latter is them and Jon "graduating". So Bendis likely has between next week (Legion issue #1) and the start of 5G to tell "freshmen" Legion/Superboy stories. For those not sold on some of the look for the Legion, this likely means new, young adult looks are on their way. So like say, Timberwolf might drop his "freshmen 15" and look a little trimmer. Stuff like that I imagine. Early on I remember Bendis very clearly stating that the looks we have seen for the Legion will be changing.
Also, just from a craft standpoint, this means that we would've effectively gotten the longest origin story for a character that I've ever seen. That's all the way from Man of Steel issue 1 to 5G Superman issue #1. It's almost like the world's longest backdoor pilot. And to my knowledge, no other 5G hero that we know of is getting that sort of lead up. Just a thought.