I beat the first season will be a 8- 10 episodes of highly produced bottle episodes. They go through all the themes of living underground in a society stuck in semi-facist 50s America. Race, gender and wealth inequality will be highlighted as if the show was an indictment on "Middle America". Critics will love it, the Alt Right will complain, Fallot fans will be blue balled yet again.
The final 30 mins of the 1:10 hr finale, the surviving female main character will emerge from the vault. I say suriving because their will be a lower class uprising that inadvertently kills most of the cast. Maybe an experiment(s) gone wrong?....FEV testing????
Our female protagonist will be captured by the Enclave. End season. We later learn in season 2 that the Enclave orchestrated the whole uprising and wanted inside the Vault. Something something about pure genetics....white race...the Vaulters are great FEV candidates for the creation of the superior race.
If it gets a season 3 it will be Fallout in name only.