I think that the Enclave still lives, but is at the final stand: if Beth want to take them back, I hope it will be in Chicago then, but the book is possibly at the end.
If, for some reason, the Enclave and the BOS return for one last showdown, I hope they both will annihilate themselves, or at least mutate into something new: in the end, the Brotherhood and the Enclave are the same coin, a last breath of the Old World.
The BOS been the technology of the past, remaining attached to values that are slowly killing them, while the Enclave is just the spirit of something that will never return, and even if technologically advanced, they will never live long enough.
Both have to end or change, this is my view.
They got to forget the past, let go, and start anew.
Also, you can join the Enclave in 76, even if without actual true members, made exception by that funny guy of MODUS.