There is very little chance of Charlton "stepping up big time".
Charlton Comics was financially weaker than both DC or Marvel.
Charlton's comic business was based entirely around it having unused printer capacity which they used to churn out comics. Comics were incidental to their business model. Indeed, when their printing machines became old and couldn't be used anymore, the company sold off its IP and left the comics field rather than invest in it.
Charlton had far worse distribution than DC and Marvel which limited its ability to build brand identity or keep loyal readers.
Without the "Marvel Age" of comics, one wonders how long the superhero boom will continue. Marvel not only produced well selling superheroes, it gave comics an allure with the college age kids and pop culture that boosted the comic industry overall. There is little evidence that absent Marvel that Charlton would ever develop and push its own "action heroes".
The leadership at Charlton was much weaker than what Lee provided at Marvel. Charlton was never an innovator, but always a follower. The artists and writers who worked there were either people who burned their bridges at the big two (like Ditko) or brand new creators who were entering the field.
The most likely scenario is that eventually the Silver Age superheroes of DC fail just like the Golden Age did, and those comics stop publishing sometime by the early seventies. The mainstays of Superman, Batman, and Wonder Woman continue to publish though. DC Comics still remains and simply switches to producing other genres, probably with a bend towards horror and scifi because that's what we saw even IOTL. It's still possible people like Denny O'Neil, Neal Adams, Jim Steranko enter the field and shake things up in non-superhero comics for DC. When the other "major" publishers fail, DC likley picks up their IP which means DC Comics more or less becomes a de facto mainstream comics monopoly. Sales likely begin to decline and collapse in the late seventies just like they did IOTL, but without Jim Shooter's Marvel there to revitalize sales, comics as an industry may end up dead far earlier than its limping corpse is now, and the comics IP used to produce low budget syndicated TV shows and cartoons.