This is 100% true, you always go after the top dog in the market. In the corporate world, Apple has nothing to lose and can only gain ground. That ground will have to come from RIM/BB. I dont see it happening, at least not with this iteration. The iPhone is good at what it does and for its current target market. I am sure we all have played with them, they look slick, but its just not the device for me. They have sold well, so there must be something to it.
Where Apple may pick up some ground is in the Prosumer market. Companies that have large deployments of BB with one or multiple BES servers are not going to dump the entire infrastructure to deploy iPhones. A corporate BB solution is SO much more than just handing out handsets. While the iPhone MAY support Exchange Active Sync, that would require very security conscience companies to support a hole in their firewall in order to support Exchange Active Sync remotely. Again, I dont think alot of large deployments are going to do this.
Apple needs to have a VPN client on the iPhone (not sure if there is now or not) or needs to develop some sort of BB Connect solution (which probably requires a license from RIM, and since the BB OS is CLOSED, RIM can control how it allows potential competition to access its market base). I think the other solution is for Apple to develop its own, similar to BES corporate solution. I dont see many CEOs out there saying "lets give all our sales guys iphones so they can listen to music and watch video". The BB give them all the business tools they need to do their job outside of an office.