As far as book sales, there’s always a chance that Titans/Teen Titans could become DC’s premiere team again. When Johns’ was writing the book it was outselling JLA and Wizard Magazine named it the best team in comics. So there’s always hope that a big name creative team will want a shot at them. I’m sure the cartoon helped raise a whole new generation of fans, many of whom are trying to be comic book creators.
As far as in continuity, I don’t think they’ll ever be the premiere team. The Justice League is made to be the All Stars of the DCU. The modern pantheon. While Titans is supposed to be the next generation. The embodiment of superhero youth. Unless DC shakes things up and puts Superman and Wonder Woman on the Titans, they aren’t going to be the top team.
Titans has something the other team don’t. Titans more so than any other DC team, feels like a family. We’ve all had best friends who are basically our brothers or sisters. People you’ve grown up with and who always have your back. That’s the Titans. I hated how that all got lost in the New 52 and I’m very glad it’s back. Justice League are coworkers but the Titans are family.
Yeah the down side of the team is that they will always be stuck in that coming of age territory. But luckily for DC there will always be young fans who can relate. The older fans may not like that the team never ages but that aspect will (hopefully) appeal to younger fans.