Microsoft has said they are not developing Office for the iPad.
They seem to have forgotten their own history. The GUI Office apps and Windows itself were highly informed by developing for Macintosh. Today's Microsoft is large and rich enough that they shouldn't need Apple to teach them anything, but what better way for them to establish expertise in touch-driven casual computing than to assign teams to dive into the leading platform?
Microsoft now has a more isolationist approach to R&D; investment, preferring work that supports already-successful lines of business and working closely only with allies or "partners" that they can control. But they established those dominant business lines by keeping their enemies even closer. Not only with Windows (twice, considering OS/2) and Office, but SQL Server also began as a partnership with Sybase.
Sun Tzu would not be impressed by this shift in strategy.