BlackBerry promised BBM for Android and iOS device earlier BBLive event. According to the schedule they should hit the app store by the end of the summer. According to a report from BlackBerry OS, BBM Beta test is going on and select individuals are testing the beta app of BBM for Android. Early screenshots of BBM on Android have already appeared on BlackBerry OS site.
According to an official response from BlackBerry to Engadget BB employees are already testing the beta versions of the app for Android and iOS and select few Android users are invited to test the app, and those slots are now full. That means we can expect the BBM for other platforms very soon.
According to the BBM Beta invites users need a device running Android 4.0 and up and BlackBerry user ID.