RIM has been working hard on the transition from the legacy OS to the new BlackBerry 10 OS. One of those obstacles the company has been tackling is the transition of their BES service which is one of the services that made the company successful. With BES 10 RIM is working to bring the service to more than just BlackBerry devices. The slides that Kyle got his hand on over at BlackBerryCool hint a release in May 2013. That seems to coordinate with the same time RIM usually holds their BlackBerry World Event. This would make sense since RIM started this event to showcase their enterprise tools among other services.
Though the dates make sense those dates can always change.