Outcome of relationship at the end of 'Blue Valentine'

Since it's my all time favorite movie, I've done a lot of research on this one. As per your question, movie ends when Dean walks away crying from Cindy and Frankie. And the ending of the movie is left to viewers opinion. It's an open end.

In the end, Cindy cursed Dean that she wants a fucking divorce and Dean tries to convince her and tells her that he doesn't want Frankie to grow up in a broken home and Cindy tells that she needs space but she doesn't persists that she wants a divorce.

So, based on the scene I mentioned, as an optimist, I thought Cindy and Dean would get back together.

Now, I'll tell you why Derek Cianfrance (director of this movie) wanted to make Blue Valentine and what he has in his mind. In an interview, Derek was asked whether his parents were divorced and he answered:

Yeah, when I was 20 they split up. It was so confusing to me that I decided to confront it with a film and just started writing it. I had various co-writers over the years, including Joey Curtis and Cami Delavigne, and they are also children of divorce, so we tried to confront our fears and confusion together. And then when finally Ryan and Michelle became a part of it they too are children of divorce, and they eventually became what I considered to be co-writers on the film.

By the above answer, it is obvious that he wanted to make a movie about the problems in marriages and how it ends with a divorce.

In IMDb trivia, it mentioned;

Some have speculated that Dean and Cindy have ended their marriage. One of the photos during the end credits shows Dean and Cindy running backwards holding a sign with "Is This You?" on it, hinting the upcoming dissolution of their marriage.

In another source here states that;

Their love has gone missing, and Cianfrance leaves it up to the viewer to decide what happened to it. He empathizes with both characters and doesn't ignore the maddening reality that a relationship, like fruit or eyesight, can go can bad from nothing but the passage of time.

And Derek Cianfrance said;

"To me there's no one reason why Dean and Cindy split up," he said. "It's a million reasons, and then at the same time, it's just a feeling."

In the question, you asked, "does it mean anything else as you think?" and despite all the speculations above, I think, Dean and Cindy will get back together.