First, RIM promises future Blackberries will run Android apps. They'll appear in 2012. Second, these future Blackberries will run the same OS that is currently powering the Playbook, QNX. So, legacy OS users will be left out. You gotta do what you gotta do.
As an Android user, I don't know how I fee about that. I'm very territorial. There's a two-year old in me that doesn't like sharing. As an Android fan, I'm not happy about it. But as a mobile warrior, I know this could be ncessarily to keep RIM chugging long and provide competition to Apple, Google, and Microsoft.
At the end of the day, I don't think this is a good thing for RIM's future to do this. Then again, it may not have a choice. I reckon this is just to hold the interests of users over until they can find a buyer. Developers cannot be too thrilled or interested in develop for Blackberries in the future.