I was talking to a few of my friends about this recently, I was thinking, at this point I don't think anyone can contend with the strawhats anymore except for the admirals and the yonkou, especially after zoro's fight with the snow woman I realized that they are really on a whole different level.
Though I can't help but think when their next big battle will be, a battle where they actually have trouble with their oponents and are considered to be weaker then their oponents! Something similar to the alabasta or cp9 showdown (alabasta zoro almost died, cp9 luffy almost died).
A fight like this is inevitable, who do you think their next big foes will be ? My bet is Big mom.