It is almost impossible for a guy and a girl to remain "just friends". One of them usually has some type of romantic feelings toward the other one. Although friendships can last many years something usually happens to end this friendship. It is completely possible for a guy to get out of the friend zone. This usually happens when a girl previously wanted to be "just friends" but has had a break up and needs a shoulder to cry on. That is usually the point where the friends become more than friends but be careful as it can ruin a friendship altogether.
I think it is possible for anyone to get out of friend zone. Guyz usually can't get out because they have usually grown up with their friends and feel connected to them. To get out of friends zone they have to change their ways of life that connects them to those friends.