The victory over Cena was big for Kevin Owens, but it still didn't in any way feel like a "He's a star for life now" sort of victory to me. It was still a midcard match that they had all of two weeks to build to.
A heel JBL once beat Cena clean in a street fight at Great American Bash 2008, but barely anyone remembers it because the victory was made insignificant due to the fact that it was only one match, and every other time they fought before and after that one match made it clear that JBL wasn't on Cena's level. Likewise, if they treat Owens as just another "monster of the week" for Cena to overcome by having him lose to Cena tonight and then for a second time at Battleground, his victory over Cena at EC won't mean anything in the long run. (Thankfully, my gut is telling me they have bigger plans for Owens than that, even though he's probably losing tonight.)