It's not a remake in the sense of taking the old story and updating it. This is taking the characters from the original story and showing them in another time-frame (like the new Voltron series is taking place after the original Lions version while the original pilots are still alive). In this case, the writers are exploring what happened before the events in the '80s series.
Yeah, it actually is a remake.
Apparently, the story will focus on 2 planets at most, and is going to streamline the story from the original while also making it darker and edgier. (Such as *Gasp* Slavery? On third earth?! OH THE MORALITY!) and..stuff.
Fights to the Death and all that.
Darker and Edgier indeed..not that that's a bad thing.
A few things have changed, too, like Lion-O and Tygra being Brothers, with Tygra being the older brother. Lion-O, however, is the one to succeed the throne, so they have a sibling rivalry thing going on.