" So, what's the consensus on the ending? Was the wormhole still open?
I tend to think it was closed.
Cooper left the station on his own to head out into the abyss, which is important for a few reasons. It was revealed earlier in the film that Cooper was an anachronism - he was a creator and a dreamer in a world that was simply subsisting. At the end of the film, his character is still an anachronism, as this new generation of humanity offers nothing for him. He's isolated and alone in this future, so he leaves. This is important for his character, as it shows his detachment from society, which simply doesn't work if humanity can follow right behind him through the wormhole just a few moments later.
Additionally, this reinforces the principal theme of humanity as explorers. Cooper knew it was statistically unlikely that he would ever find Brand, but the point is that he was heading out into the unknown to do so. He was heading out to embrace this intrinsic human desire...not to cruise down the paved path of the wormhole to a place he's already been. "