While Microsoft's development cycles have increased in recent years, one thing is certain: Microsoft will eventually release Exchange 12, and there will certainly be some things that you need to consider before rolling out an upgrade. Yes, it’s early to be thinking about Exchange 12, but a little forethought now may help you a whole lot when the time comes when you organization needs a whiz-bang new feature found only in Exchange 12.
First, if your server’s processors are of the 32-bit-only variety, you’re going to be out of luck when Exchange 12 rolls off the production line. Microsoft recently announced that Exchange 12 will be supported only on 64-bit platforms, along with an eventual release of Longhorn Server R2. If you’re currently making plans to replace or add hardware to support your Exchange infrastructure, make sure whatever you buy is capable of handling a 64-bit operating system. Any currently shipping x86-64 (or a 32-bit processor with 64-bit extensions) will do.
When it comes to public folders, there have been rumors that public folders as you know them will be phased out in Exchange 12, with SharePoint picking up the pieces in some form. However, I doubt that this will be the case in Exchange 12. That said, Microsoft will likely soon to begin to push SharePoint for tasks currently handled by public folders. From everything I have read thus far, you can expect Exchange 12 to be the last version that supports public folders. Do bear in mind that everything is subject to change! Why do I mention this? If you’re considering planning a significant business process around the use of Exchange public folders, consider using one of the various versions of SharePoint instead. By doing so, it’s less likely that you’ll need to undertake a project to revamp the process in the next few years.
Microsoft has big plans for Exchange. With a little foreknowledge and planning, you can make decisions that will save you a little pain in the future.