With the possibility that RIM shuts down, or is split to pieces and sold for scrap, there is a probability greater than zero for some kind of disruption of Blackberry-related email and messaging services.
This is true for all smartphone OS vendors. If one shuts down, or decides to close the business unit, our smartphones would become something very close to a brick, only much more expensive. Sure, we could still use them for basic activities like phone calls and texting, but all the functions that make smartphones smart would disappear. App stores, push services, and all the like would stop working, not to mention OS updates.
I can’t see Google or Apple dropping out of the smartphone business any time soon, but for Microsoft I still have some doubts. Windows Phone is not yet widely-adopted and no one knows for sure if it will ever be. Time will tell, but I believe that if within one year Windows Phone will still be a rounding error in smartphone purchase stats, then existing owners should start to worry.
Meanwhile, Nokia phones sold in 2001 are still working perfectly, and will probably keep going for the next century or so.