There are heretical "gospels" that say all sorts of things. Like most, this one is four hundred years removed from Our Lord's earthly life. Why would even a non-believer take this seriously?
I don't know if it is so much non-believers that care about this stuff. It is those who identify as Catholic that made The Da Vinci code such a hit. Prots and non-believers aren't as fascinated with church history and any potential mysteries as those who have grown up steeped in so called "cultural Catholicism."
Your average, modern, liberal Catholic would just love to have something they could use to say "See...the church was wrong about this (Jesus' marital status) so it could also be wrong about gαy marriage, birth control etc. Jesus loved everyone, we should accept everyone, tolerate everything..."
Read this is this morning, from a "Catholic"
Who would have thought initially that Dan Brown's novels would have provoked the responses they provoked from institutions like Opus Dei, assorted bishops and cardinals, and the subdean of Westminster Abbey! WHAT IF Jesus had married, had married Mary Magdalene, made babies enough for a championship football team, and retired to a small cave in southern France -- after the ascension of course!
Religion has long been a fertile ground for a transcendent brand of doctrine styled "my way or the highway" theology. That's how we silence people who disagree with us, or just plain get rid of them, as in bonfires and gas chambers. 'Tis a bit early for anyone to prognosticate how this discovery will "change" Christianity, if it does at all. Whatever may come of it, perhaps it will become a personal invitation to all to leave their good Christian lives and follow Jesus, who may (or may not) be a husband and daddy.
As far as the "finding" itself? I was a young teen when I saw The Da Vinci Code. Unfortunately, I did seek out the gnostic "gospels" and wanted to see if Jesus really did kiss Mary Magdalene. It is crazy how media can mess with people.
When my bff got married, she had major problems with her priest (this is the priest that later ended up helping me back to the Faith) and after the ceremony was over she decided to basically taunt him and tell him that it was her belief that Jesus loved Mary Magdalene so much, that he gave the church to her, not St. Peter. Peter, she believed was just as much a "misogynist" as Paul (this was her words) and he couldn't stand it that Jesus was a feminist, so he "stole" it back.

You might be shocked at how many people believe things like that.
http://www.gnostic.info/rose_Mary%20Magdalene.html