I'm a long term scout leader and I've predicted this for a long time and its a good thing.

1. Society has changed. People want family activities.  Everyone doesn't live in a dad and boys, mom and girls division anymore.
2. Explorer and Venture scouts allow girls 14 and older and have for years.  The girls love it and they are great at it.  Many scout camp counselors are girls as well. 
3. We live in a society where your boss may be man or woman.  Your team members may be male or female.  You may be a manager of a whole team of mixed sexes.  In Boy Scouts we try to teach leadership and team work.  This makes it more real world.
4. Scouting needs to maintain relevance to the adults we need as leaders and to the kids we need as participants.