If there’s a Season 2, it’s gonna be some time after DLC 4. My guess is it would start in september.
However, I’m not sure if we are gonna be getting more than 4 real story campaign DLCs and those are all part of the first season pass. I think after that they’ll mostly just add some smaller stuff, like my guess is we are gonna get another 2 Takedowns, maybe some standalone raid bosses, limited time events etc.
Then they are maybe gonna sell a few small content packets equivalent to the Headhunter Packs of Borderlands 2 and at some point they are probably going to start to sell some cosmetics to keep the game alive and profitable for a bit longer.