I actually don't think the Blackberry is very threatened by the iPhone. The iPhone is all about the chique factor and gives up on some functionality. There are things like push e-mail that are literally battle tested that the iPhone just doesn't offer. That's why the RAZR has way more to lose since it's all about the chique factor and looking cool.
Thinking about it now, I actually wouldn't be surprised if sales of smartphones in general go up. The iPhone is awesome, but it's not RIDICULOUSLY awesome. Ok maybe a little bit. But there are other devices that do comparable things as the iPhone and at a cheaper price. Apple is bringing a lot of attention to the whole smart phone category and there will be people that go with something other than the iPhone.