This is an interesting article published by the Washington Post. It discusses some key points that Unions can follow to survive in the tough anti-union atmosphere. This article bases its arguments on scholarly published articles.
The problem that I see is that Unions must represent all employees, regardless of membership. Any changes would have to occur at the legislative level, which means: it will just not happen.
The underfunding of Unions continues to be a big struggle. How can you get enough staff to represent members when there is no money to pay them? RTW laws are a slippery slope.