The percentages are getting smaller every year for young women to identify as feminists. This does not mean that feminist ideas are any less mainstream, just that it is absorbed into the daily lives of people. As actions are taken that further feminist causes by the second and third waves, they are simply absorbed by the fourth wavers as a matter of course, instead being discussed.
Feminism as a word is being used less by the younger crowds (16-24) because there is a growing stigma attached to it. Young women are finding it harder to attract mates after declaring themselves to be feminist. This doesn't mean that they aren't living it....just that they refuse to say it. Many identify as "equalist", "humanist", "egalitarian", and the like.
As the second and third waves grow older, there may be a renaissance of the type of activism that brought about many changes by some of the more outspoken young women, but I think it will be much smaller than the original movement. The state is now the primary director of feminist ideology in Western Culture, and it has a vested interest in continuing the types of programs that feminists have rallied for in the past. These programs are now accepted by the mainstream population as "normal" or even "needed", and votes depend on the continued government expenditure of these programs.
This is likely to continue in any case. The tug of war between traditionalist culture and feminist thought has slowly pulled the way of feminist thought in universities and the halls of power of the last 40 years. As more young women come into their own, they are coming into a system that is already geared to give them a hand......so they know not the struggle of their parents and grandparents, and are less likely to see it as an "active" means but rather just another way of life.
In the end, they may not call themselves feminists......but they have a tendency to hold similar values.