Does Microsoft have big plans for Office Mobile apps - Word, Excel, Powerpoint, Outlook. And why is To-Do app not part of them, like in Web and Win32 versions?
If it's any consolation, Microsoft hasn't done any major changes to the Office Suite on iOS or Android either. They've added some functionality that we've enjoyed on Windows phones from the beginning. If they stay on their present course (2007, 2010, 2013, 2016...) you won't see any "major" changes until 2019 at the earliest. This would coincide with mobile's Last Rites.