This could ultimately be the end of Office, but at the moment, Rich Text docs and spreadsheets still rule the enterprise. And as far as that goes, with strong Excel-SQL Server (or other database), integration for data analysis, Excel may be the strongest product in the suite (and Excel might very well be the reason Office is so strong in enterprise).

I think this situation could change rapidly, but MSFT has the momentum, and I could also see Office remaining out in front. It's difficult to imagine someone coming along and supplanting Excel with something superior at the moment.