Firefox would do themselves a huge favor if they were to solve their memory sink issue. If they were to adapt some of Chrome's technology to increase its speed while maintaining core fundamentals, they would probably get a good edge. Everyone will always have browser preference so it's not unlikely that a few people will stay but it's getting to the point where Firefox will be similar to IE without all of the issues. It's not hip, it's not up-to-date... it's not sleek enough or well broadcast...
Kind of hard to compete with Google's marketing as well.
I personally like FX, it's been faithful to me and I love my modifications. The tree style tabs, the look and feel, it's just what I'm used to I suppose.