I don't know the exact number of "forever maintainers" but I'm sure there are several numbers floating around online. The NWCR that lin43 references might be a good source for info; also, the book "Thin for Life" probably has some numbers - but also excellent strategies for how long-term maintainers do it.
I made a conscious decision a long time ago not to think about the percentages. Maintaining weight loss is very, very difficult (for me, at least, and for many others, but not for everyone). But you know what? I've done a lot of stuff in my life that other people haven't done, or that only a small percentage of the population has accomplished. I have a graduate degree. I've lived long-term in a foreign country. I've accomplished things in my personal life . . . those aren't based on "odds." Those things were difficult and I struggled, but I accomplished them. Why not weight loss maintenance?
As for skin removal - it's not inevitable. The general consensus is that no one knows what you will look like after weight loss until it's happened and maintained the weight loss for a year or so to let things "settle." There are people on the boards who've had skin removal surgery and many, including myself, who have not. I will say that I'd rather deal with extra skin than with extra fat!