Tons of teens are into that stuff (I've only recently left that age group, and god knows I was), but I can't imagine a morning timeslot being very successful, given that very few are going to wake up early just to watch cartoons, and like rosiv said, if they have an internet connection and much brains, they wouldn't have to even if they liked the show.
"Teens/Adolescents" are a tough audience to target because people change dramatically over that time period, and at very different rates. Some are going to hang on to "kid's" stuff forever (especially as long as "ironic nostalgia" is the hip thing) and some are going to gravitate toward books and movies aimed more at adults and the college crowd. In fact most people will do a bit of both. Teens are a huge and varied group, and while their disposable income makes corporate execs drool, it's nigh-impossible to appeal to all of them at once, so it can also be pretty elusive.
The animation age ghetto is also still pretty strong in the US, if less so than it used to be, so while importing stuff like anime for that age group makes sense, actually backing the complete production of a show is still a very risky proposition. Animation ain't cheap, and young kids are the only really reliable audience, since few of them have easy, unrestricted internet access, but finding what they want on TV is simple. So the shows that succeed are either aimed at them (with the possibility of the smart ones having massive broad appeal a la adventure time), or they're produced as cheaply as possible by necessity (see adult swim shows). Content-wise, what succeeds with teens tends not to be the shows "aimed" at them, but the ones that focus on being good or funny or... whatever they are that appeals, and bringing some subset of the age group into the audience.
It's not like producing good animated shows aimed at teens is impossible, plenty of anime have been doing it for years, and A:TLA/Teen Titans were things, but I can't imagine them being nearly as successful if they'd aired on Saturday morning, when most teens are asleep if they don't have a good reason not to be.
tl:dr; few/no western producers would do something as risky as backing a for-teens show that could alienate the younger audience (A:TLA toed the line , but still made some obvious concessions to that effect, as do most action cartoons made in the west). And even if they did, it would be crazy to only air that only on a Saturday morning time slot.
