AEW got about 177 people including commentators and management on contract. That may seem like a lot but compared to WWE thats about the average for a major promotion, they have 4 slots of programming weekly.
Dont forget unlike WWE, the talent is also working for other companies (Bobby Fish for MLW, Keira Hogan for NWA, Mox and Archer for New Japan) so I dont think its that bad of a situation. For sure theres people that are gonna be unhappy but they can also ask for their release or have the indepedent contractor option/forbidden door
Now if theres a situation where Tony is keeping from that, thats another story.
As for WWE, even with all these cuts last 2 years, they have like 5 rosters (Smackdown, Raw, NXT, NXT UK, 205 Live) so I dont think they'll kill any brand splits