The iPad Pro, with its optional stylus and keyboard-cover, should be a fine machine to run Microsoft's Office apps for iOS.
And it probably will be, but there's a catch. The Office apps on the current iPads offer both viewing and editing documents for free. A handful of features require Office 365 subscriptions, available as in-app purchases, but the core editing capabilities are all zero cost.
Install those same apps on the iPad Pro once it arrives in November, however, and all those editing features will go away. Office on the iPad Pro will require an Office 365 subscription for any and all editing.