There's some pros and cons in this move I guess.
From a TV standpoint, Nickelodeon's a big company with deep pockets and resources so they can really put as much as needed into the new cartoon. And the new series can get a whole lot more exposure and promotion than the 2K3 series did, because Nickelodeon's such a force. However, I'm guessing it won't be able to run past 65 episodes (maybe a good thing, maybe a bad thing, depends). Multiple iterations can change that though. I was actually hoping for a CG cartoon to differentiate from what came before, so off to a good start I guess.
From a movie standpoint, I'm guessing this dissolves any hopes fans had of seeing a PG-13 TMNT movie (I think the chances of that planned live-action one being PG-13 were slim to none anyway, what with 4Kids having been on tap to handle licensing). Still, I imagine Nickelodeon will be willing to put a lot of effort and resources into it, as much as needed to make it a success.
From a comic standpoint...??? A big question mark and I'm sure a big cause for concern and uncertainty in the fanbase, although the comics were getting like zero exposure at this point anyway. Who knows what this means for that area. Probably not good things.
But now, all control is out of the creators' hands. That's kind of worrisome. Nickelodeon will definitely be a lot more willing to reach into the 80s series for characters and concepts, however, which is something Laird was never into. There's always two sides to this kind of thing.
Probably the biggest thing that will cause people to worry is that TMNT is now just one of Nickelodeon's many, many properties, instead of being the cornerstone of Mirage. It wouldn't be nearly as worrisome if Nickelodeon had simply acquired TV rights rather than being the entire property lock stock and barrel. So TMNT has a future with Nickelodeon for the foreseeable future but there's less of that certainty that it will come back after it fades again, after X amount of years. But that's looking a good like 6-10 years into the future, so who knows.
Anyway I'm sure Gary Richardson is leaning back in his chair with a big cigar right now.
Yeah, I think it's safe to assume the new cartoon will be a companion to the new movie, directly or indirectly.