Pick a vein and get to work
According to multiple posts from the Bethesda family of social media presences, Fallout 4 has no level cap and will not end once the main storyline is complete. So, if you were so inclined, you could spend the rest of your life turning your Vault Dweller into the very embodiment of the wasteland; consuming everything that lives, leaving piles of corpses in your wake.
This is a welcome change after Fallout 3 and Fallout: New Vegas‘misguided “no more playing this after the credits” decision. Bethesda eventually released a DLC pack for Fallout 3 that allowed the player to continue past the conclusion of the main narrative, but you had to pony up if you wanted to see how your story ultimately affected the Capital Wasteland.
Skyrim managed to avoid this issue by treating the main story as just another quest to be completed. It made the threat of Alduin feel like part of a larger story, which is no bad thing. Bethesda crafts enormous worlds for their players to explore — nothing makes a place feel massive quite like the sensation of being out of your depth. We’ll have to see how this is handled in Fallout 4. Y’know, because the game’s not out yet.
To our fans who’ve asked: Fallout 4 doesn’t end when the main story is over and there is no level cap. You can keep playing and leveling.
— BethesdaGameStudios (@BethesdaStudios) August 6, 2015