"Twenty years from now there may no longer be [ERISA] class actions.... A series of recent U.S. Supreme Court decisions ... indicate that ERISA plan sponsors who adopt mandatory arbitration provisions with class action waivers for employee benefit plan disputes may be able to eliminate all future ERISA class actions. Accordingly, every employer should assess whether the protections afforded by arbitration agreements coupled with class and collective action waivers outweigh the potential disadvantages."