I wouldn't call Blackberry similar to Palm as they are constantly churning out new models, features etc. Palm did themselves in sticking with OS 3.5 for too long and not seeing the demand for a true wireless mobile device.
I think the core issue with this "debate" is you are talking about two totally different markets .. corporate world and general populace. No doubt mobility is going to see huge gains over the next 2 years and the mobile world changes at such a rapid pace I don't think you will ever see a dominate piece of hardware. Once the new networks light up (2010 timeframe LTE, HSPCA etc) who knows what type of devices will be out.
I think if you look at all the Fortune 500 companies that have mobile solutions and have a BES, they recognize it's value. I know a lot of people across different verticals and the verdict on Iphone is the same - "Wait and see, we have some to check out but it's not quite a Blackberry yet" We understand the coolness factor, we see the potential in new functional it brings etc .. I can't budget and plan on potential. If everyone is thinking OS 2.0 is going to be this huge shift and make the iphone that much better .. prepare to be letdown, blackberry enterprise intergation is heads above OS 2.0 I'm not even sure in it's current build if it will be ready for June.
I'm also wagering you will see a Blackberry Connect client for the Iphone by the end of the year. Apple Fanboys want so badly to say "we won, we're #1" that they are riding the iphone like crazy and will not accept less then that. The mobile world is dynamic and many factors come into play:
Networks (realiablity, speed, coverage)
Ease of deployment, upgrading
The current Iphone will likely be dead by 2010 if not sooner, I'd wager they'd sell out the channel to favor the 3G version and then introduce another less cost model later this year with maybe 4gb storage (plenty for the average cell user)
At the end of all this your talking about two fairly large companies with a good asset base and both likely have a 2, 5, 10 year business model.