Open endings are tricky I think they can work if they are used correctly but a lot of the time it might end up feeling cheap and pretentious. I mean look at how much people still hate the ending of the Sopranos. There is this book called 2666 by Roberto Bolano, which had a very open ending. It felt well earned because it was as if we were just seeing a snapshot of these characters lives. Conversely, I was not thrilled at all with the ending to Swan Song.
While we are talking about endings something I hardly ever get to see but would love to is a five year later epilogue. I want to see how these characters that I've come to care deeply about are living their lives.