There's talk of a Microsoft Office - Word, Excel, Powerpoint - app come the new year, but last I heard, they were thinking you'd have to be a subscriber to their online Office 365 (
Office Online Services - Hosted in the Cloud - Microsoft Office 365) to be able to edit with it. Otherwise, it would be just a viewer. Seems they are keen on guaranteeing failure with that proviso - I know a number of people who would be keen on an iOS suite that would create/save/read to Microsoft Office files by default, rather than, say, Pages - but who won't invest in yet another word processor program to do it.
In the meantime however, there is the free CloudOn app, which offers a 'virtual' online Office environment that can access and edit files stored in Dropbox, Google Drive and Box and it's okay.