The NieR series will keep going so long as its creator is alive
As long as Yoko Taro is still kicking, we're not going to see the series come to an end.
At a recent presentation as part of the South Korean G-Star conference, Nier: Automata producer Yosuke Saito spoke about the game's development, giving interesting titbits and anecdotes about how the action game came to life.
At the end of the talk, Saito also spoke a little bit about the franchise's future. As reported by 4Gamer and shared in English by Genki_JPN, Saito didn't reveal what any new games would look like, but said that the series will not end so long as its creator, Yoko Taro, is still alive to work on it.
There was a hint at an unannounced collaboration that Saito hopes he can talk more about next year, but for now we at least can rest easy knowing the series will continue.