Without going into the speculation what Nokia or Blackberry will do in future products, IMO there is only one reason for adopting Dalvik in any mobile OS - to be able to migrate to Android while keeping the current developer/userbase and their software investment. Why ? Because the moment Android apps/services reliably run on a device and can be bought from the Android Marketplace, there is no reason for any new developer to even think about doing anything native for that particular platform. This is turn means that on the long run you have the same apps/services as your competitors, but you have the monetary/time burden of maintaining a full OS and a compatibility layer IN ADDITION to what every Android vendor does. That's why HTC/Moto/etc do Sense/Blur et al and not take a full OS and put Dalvik on top - it would be an overkill with no benefit.