To be fair, I think that’s just re-releasing all the old material.
Definitive Edition - has twelve heroes, six villains, and six environments. I predict it’ll be the ten original core heroes plus Unity and the Scholar, the four original core villains plus Ambuscade and Miss Information, and the four original core environments plus Omnitron-IV and Silver Gulch.
Big Box 1: Rook City and Infernal Relics [12 decks]
Big Box 2: Shattered Timelines and Wrath of the Cosmos [12 decks]
Big Box 3: Vengeance [12 decks]
Big Box 4*: Villains of the Multiverse [14 decks, but no heroes so not as many cards]
Big Box 5*: Standalones. Seven heroes (Benchmark, Guise, Stuntman, and Void Guard) Two Villains (Chokepoint, Wager Master) and Two Environments (Celestial Tribunal and Final Wasteland.) [11 decks, but more hero-tilted]
[* - It’s possible that they’ll rearrange Villains and the Standalones to balance them out a bit more; maybe five Vengeance-style villains, one standard villain, three or four heroes and three environments per set.]
Big Box 6: Oblivaeon. [14 decks: five heroes, five environments, and four Oblivaeon-specific decks.]
That’s a full six boxes of re-released Sentinels material without actually having any new decks.