Joel and Clem. Together forever. One way or another, we have a feeling this is going to be true. At the movie's close, our protagonists, despite knowing that they have already tried and failed to have a successful relationship, decide to get back together and give it another go. The big question of whether or not things will work out is never answered.
More pessimistic people may be inclined to think that our couple will be trapped forever in a cycle of love and hate; falling for each other before things get sour and then erasing each other from their memories, over and over again.
And while that could happen, optimists could see the fact that Joel and Clem are aware of the fact that they've already had the Lacuna procedure as evidence that this will not be cyclical. If things don't work out this time around, would they really decide once more to have a procedure that essentially only managed to cause more pain in the end? And on second thought, with Mary mailing all of the patients their information, is Lacuna and its procedure really going to be around too much longer?
Who knows? Maybe the procedure is here to stay, an effective way for all couples to finally erase their time together. Is it sad? Scary? Wonderful? Depressing? Happy? It's all a matter of perspective.