Nope, its fresh thing that come out just like that, without any leak. At least I haven't come across any.
As for the need for a remake - yes, the anime definitely needs it. It started being released at a time when the old animation model was ending (it's about the number of episodes, not their quality) and that's how it continues to this day. Archaic.
Oh, I completely understand, WIT Studio did a very good job with AoT back in the day, so surely this remake will be of high quality.
I hope so: )