Turtles makes them a ton of money. That's why it's their biggest push these days, and TMNT has always been a money haul.
They've shown plenty of prototypes that haven't seen the light of day. There have been teases of Bruce the shark from Jaws for years with prototypes, and we might actually see it in a few more years with them putting out JAWS figures now. But then who knows.
I've learned to never expect anything from NECA until we've seen actual production/promotional stills of a final figure. There's plenty that never hit the shelves because they never make it passed the prototype stage. Happens with a lot of companies.