Apple's yearly developer conference should see iOS 8, OS X 10.10, and likely some hardware.
Microsoft Leaks References to 'Office Mobile for iPhone', 'Excel for iPad' and 'PowerPoint for iPad'
As noted by Mac4ever, references to several Office for iOS applications have begun creeping into Microsoft's support site, albeit as product tags that appear to have been applied improperly to support articles.
One example is a document addressing custom numeric formats in Excel. On the support site for the United States, the document is listed as applying to Excel 2013, while on the French support site it is incorrectly listed as applying to Excel for iPad. Searches for similar phrases throughout Microsoft's support site yield a number of other references, including "Excel for iPad", "PowerPoint for iPad", and "Office Mobile for iPhone".
While the appearance of these new product tags doesn't offer any additional information on Microsoft's plans, it does seem to confirm the products' existence and that the company is working toward building out support site infrastructure for them ahead of their debut.