I don't believe that the iPhone will ever become the dominant business smartphone, but there's little question that there's some substantial spillover happening as office workers bring their iPhones into the workplace, and even request them when it comes time for the boss to make a corporate purchase.
There is a noteworthy trend happening today, and that is consumer technology infiltrating the enterprise. Besides the consumer-oriented smartphone, complete with camera and music player, plenty of other technologies initially developed for consumers are finding a place in the office--such as instant messaging, for example.
The security guys are having a decidedly hard time with it all, but for the VARs, there is an opportunity here. You can't keep these technologies out of the workplace, so the opportunity is to help implement the technologies in a controlled way, and help formulate policies for their use.