Now that I have your attention, I want to clarify that this post is only a reflection (based on official facts) but does not count as official information.
I publish this just to talk about the Rise of the TMNT series and its future for what has been seen so far. Well, the first real indication that the series would be ending was given last year, when in none of the two most important comiccon in which nickelodeon was presented there was any mention about the future of this series (normally a popular show present advances of its future seasons, but it was not the case). Then came the announcement that the series would be moved from nickelodeon to nicktoons, this second channel being one with less audience than the main channel. By the end of last year Playmates announced that it would no longer focus on launching new Rise of TMNT products and instead that it would opt for the classic TMNT line (it is assumed that sales of the Rise line have not been good and hence the decision of the company). Recently this was confirmed in the Toy Fair since in its stand the few figures that appeared from Rise of TMNT were the ones already seen without new additions. Finally this February, nickelodeon announced its new projects and series renewals, and the preliminary list did not include the Turtles series (although it is true that even shows that are not on the list in the future can be renewed, This is not a good sign.)
With all this there are rumors speculating that the series will end soon and that nickelodeon will bring a new series immediately. Rumor has even been circulated that by September, some of the new series will be seen. And since Giancarlo Volpe (Avatar) returned to nick to work on an undisclosed project, some already dream that he is working on a series of TMNT. But all this is what people are saying (in the forums, twitter, tumblr, facebook, etc)
Personally I see quite possible / casiseguro that the Rise series has bequeathed to its end, because by now we should have an announcement from another season if it will continue (That if Nick will have the last word). Even so, new episodes of Rise will continue to arrive because the team in charge of the series will still end season 2, and the movie of this series for netflix is still standing until the opposite is said. But as for a new series I would not be surprised if Nick wants to go out with a new version, because "learn something money!", I just hope that if this is the case, this time if they take time to think and let rest at fandom
BUT THIS IS JUST A REFLECTION. IT WAS NOT STILL CONFIRMED THAT RISE OF TMNT IS CANCELED. THERE IS NO OFFICIAL ANNOUNCEMENT OF A NEW TMNT SERIES.