Toonami is one of the most, if not THE most popular blocks on Cartoon Network. Notice how they've milked Toonami so far:
A 12:30 showing of their #1 show, and a late night block of all their shows, new and old. It's like a mini marathon every week. A Toonami super chunk.
If Boomerang takes off, I don't think Cartoon Network would see anything wrong in another spinoff network. Although I'm not sure how tolerant Time Warner would be of a mature cartoon channel.
Society today has been brainwashed with the fact that cartoons are for kids and kids only. Even with more mature cartoons like The Simpsons and South Park, people aren't disconnecting the link between kids and cartoons in their minds. For the sake of argument, and so I won't have censorship groups breaking down my door for using their names, let's create an organization committed to being the world's watchdog of "questionable programming", OMSA (the Overprotective Mother Society of America). They would put up the following argument: Little kids would surf the channels, and land on CNX: Toonami and say "Hey! That looks like Pokémon!..........Mommy, why is she naked? [gasp]! No, don't die! WAAAAAH!"They'd send thousands of letters to Time Warner (cause that's what OMSA does to any company when anything, no matter how unnoticable or trivial, offends them, and it seems like everything does nowadays) demanding that CNX be taken off the air. And since they outnumber any special intrest group because they work together, CNX might be very short lived. If CNX is ever made the way we want it, Time Warner must be VERY careful with how it's marketed to have outbursts from concerned "viewers" to an absolute minimum.
Whether it's a premium channel (God, I hope not.) or a "Parental discretion advised" warning before every, it must make itself as immune from uninformed outbursts as possible.