Ok before I start this long post, I just like to say, I'm a huge fan of the marriage and always liked the character that is Mary Jane, so this post might be a little biased. This post is not a debate of whether Spider-Man should be married or not, it is about how stupid is the notion that at this point of time, the marriage can be broken.
So how do you break a marriage? Well there are 3 ways:
So when do people get divorced? It could be either one side really hurt the other, if by cheating or neglect or an act of violence. It can be a traumatic experience that cause the 2 people involved to drift apart. Or it can be just that the love is gone. The Spider-Marriage had a lot of traumatic experiences, they suffered the revelation that Peter is a clone (Which caused an act of violence, worst issue ever), they lost a baby, one side thought the other was dead, and now the unmasking and the fugitives status. Yet they stuck together threw all of this, and now you actually telling me they will ever get a divorce? I call bullsh*t. Peter will never leave MJ cause she the thing that keeps him going, and she will never leave him she knows he will always be there for her when she needs him. Any story that ends up in a divorce, let alone a story that last 4 issues (IE: 'One More Day'), is a load of bull, and will not happen. Next.
This seems like an easy solution, you don't like the marriage? Kill off the wife! Yes this wife has been part of the Spider-Man books for 40 years, has become a pretty strong character, and the last time you tried to kill her the uproar wasn't pleasant. Lets face it, Mary Jane has become a character you can't kill, she became the 2nd most important character in the Spider-Man world. She feature heavily in any of the the universes (616, Ultimate, MC-2), she been a pivot character in all 3 of the Spider-Man movies, there is a Spider-Man cartoon coming up where she will be heavily involved, hell she even have her own book. After Spidey himself, she is most untouchable character in the books, it ain't gonna happen.
Ah the most sexy "solution", whether its a mind wipe, a dream or even the revelation that the minister who wed them 20 years ago (Real time) was actually the Chameleon. There are a lot of ways to retcon the marriage, but does Marvel want to go that way? Marvel did one major retcon to Spider-Man in his 45 years long history, it was called the Clone Saga, and it was the biggest piece of sh*t they ever came up with. And even that retcon is not really a retcon, because they never erased an event that happen in a Spider-Man book. Even the infamous Clone Saga wasn't erased, they just never refer to it, it still happened. Ben Reilly and Baby May existed, just nobody talks about it anymore. I find it hard to believe that Marvel will actually erase 20 years of continuity, do the end actually justify the means?
It will take a genius to pull off an end to the Spider-Marriage, I personally can't see it happening. But in a world that Spider-Man is actually a being created by totems, who died and reborn, had his greatest enemy impregnate his first true love and recently revealed his identity to the world and endangering the life of his loved ones, anything can happen.