Damnthenet almost hit the nail right on the head. Office's worst enemy is Office itself. There are so many updates pushing forth so many new features that compatibility becomes a real pain at times. Forget about compatibility between various versions of the suite, there are issues even with the current versions and their service packs. How many users felt the searing pain of Outlook's new format PST issue or the compatibility glitch between InfoPath and InfoPath SP1? And God knows how much Office 12 is going to change.
As of now, the roadmap to Office 12 stands thus.
Beta 1: October 2005
Beta 2 (Public): First half of 2006
Beta 3 (Public): Mid-2006
RTM: Late summer 2006
General availability (GA): October 2006
Contrary to what most people think, Microsoft has clearly indicated that Office 12 is not necessarily for Longhorn. The suite will be released in 32- and 64-bit versions and will fully support Windows 2000 and Windows XP, and is not "an Office Suite for Longhorn." Since the Office Suite will be shipping long before Longhorn does, this makes a lot of sense. According to one Microsoft employee, "The Office team is disciplined. They nail down their feature set, set a schedule and usually hit it." Ouch! That's gotta hurt the Longhorn guys somewhere!
Industry analysts are of the opinion that Office 12 would be a radical change and won't simply be "Office 2003 Tweaked/Reloaded"; in fact, some are believing that by the time Longhorn ships, two versions of the Office suite, an "Office Classic" version and a special Longhorn version would be shipped. One thing though, as of Office 12, Office 97 is officially out of the picture. No more compatibility with Office 97 once it hits the shelves! Oh, yes, it would also feature secure access to public IM networks including those of AOL and Yahoo! And Excel will now come with a server product with central access to spreadsheets, reports, etc. Paul Thurott has updated his Office 12 Preview site on May 11 with some new feature lists. Check it out here.