Here's an interesting fact for you: the original April O'Neil was based on the creator's first wife, who was biracial. She was changed to be the redheaded reporter in the 80s to "boost sales" for the TMNT franchise. In fact, here's a pic of the original.
Now THAT's a badass April O'Neil. I don't care what anybody says. I like this April a LOT more than the redheaded April. I'm just disappointed that Seth Rogen didn't go with this one. It would've been an amazing callback to the original TMNT. Still, I don't mind April O'Neil being black at all or the new version for Mutant Mayhem (plus, Mutant Mayhem has John Cena).
If there's anything we should be worried about, it's misrepresentation. This isn't Disney just swapping someone out to "go with their mission". It's Paramount righting a wrong set for numerous decades. Thank goodness it's being rectified because we deserve an April O'Neil like this.