I wouldn't bet on this forever. There are increasingly good tools to manage at least iOS devices in enterprise environments, and the platform security features of iOS are nearly as good as Blackberry. In the BYOD world (which is growing), you can deal with less management of devices (enforcing some minimum standards), then layering stuff like Good on top of them to secure business applications.

In the BYOD world, very few people will be bringing Blackberries to the party.