Movies and TV Shows

Closest I can think of, despite it probably being more of a show aimed at teens and young adults, would be Ren and Stimpy with their failed Adult Party Cartoon. Other than that, I can't think of any examples.

Not sure about 'aldut humor', that would probably cross a line for networks image.

Avatar Korra was definatly more for teens than ATLA.

Ben 10 also grew up with audience, making them teens and eventually rebooting the IP to milk the next generation.

Spongebob's hidden adult humor pretty much disapeared as the years went on. (Doubt we"ll ever see something like the panty raid again).

Teen Titans go is the opposite, taking a more teenage show and making it for younger kids.

Didn't Rugrats have a version where they were teens?

Velma, although I've not heard good things about that show.

The adventure time spin off Fiona and Cake, was weird seeing fin just murder a monster and it have real blood

They didn't reboot them as shows, but Invader Zim and Rocko's Modern Life got some modern 90 minute features and they were very much made for the adults who grew up with the old shows.

To a lesser extent, the same with the Animaniacs reboot.

iCarly? I didn't end up watching it but I think they like drink and stuff

Too bad Timmy looses them when he is getting older. So no post >18 content with them.
Dunno how fun 16 y/o timmy would be.

Are there any children's shows that have been rebooted as adult shows in order to grow with their audience?

Well, there was Ren and Stimpy: Adult Party Cartoon...but we don't talk about that one.

Samurai Jack's final season comes to mind. The first couple of episodes were amazing. It took the best parts of the show and made it a lot more serious.