I've created a patch to add a new session store that is backed by ActiveSupport::Cache::Store. It has the same functionality as the existing MemCacheStore except it is far more flexible in that it can be backed by any ActiveSupport::Cache::Store (i.e. DalliStore, RedisStore, MongoStore, etc).
Lighthouse ticket:
https://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/6675