In the last year we've been aware of something we previously didn't have to consider...competition. There will be those loyal to RIM and there will be those who will go down the MS route, but the important thing to remember is that the market is big enough for all. 40% of the corporate world uses Exchange - of that 40% only 25% run Exchange 2K3 which is a pretty small group. As time goes on more will upgrade, but a jump to 2K3 is a big step for most.
I don't accept the ROI arguements for Exchange push though. Running costs aren't a worry even though the Exchange solution is more bandwidth hungry as carriers are offering competitive data bundles often at a fixed price. Where the ROI on Exchange is screwed is the arguement that states you don't need to buy a BES or a machine to install it on. People forget the devices are a lot more expensive than a RIM device, not to mention they'll take a bit more of user support from the IT dept than a BB will, and if you're going to consider costs, you must include these elements such as time supporting users.
With the carriers we'll see great change in voice calls as well I suspect - all roads lead back to a server and the time will come where mobile calls are all just VoIP, and that will fix price everything. Just image a totally fixed cost including data for email and web browsing and a fixed call spend!!! Dream on!!!!!