Yep, that's what they said -- that all the villains will be characters never before portrayed in animation, ranging from recently-created, modern villains like Pyg and Toad all the way back to obscure baddies who appeared once or twice in the Golden Age.
Although I'm still not convinced they'll maintain that practice throughout the entire series. I suspect that after a year or two, once they've given this show time to establish its own voice and identity, they may bring in some of the familiar foes.
It's a bold (brave and ?) move, it will be interesting to see if it pays off. Maybe unlike The Batman which took liberties with the mainstays people will be more open minded about this. I'm not so sure though as anything that isn't a continuation from BTAS isn't very warmly received (though a lot of people did end up warming up to Brave and the Bold).