Dictation should spread to Excel, Outlook and PowerPoint sometime in 2019.

More accessibility improvements are coming in the near future. Microsoft is bringing Immersive Reader to its Flipgrid social education communities, and upgrading the tool with both real-time translation as well as support for reading math problems. The feature is now available in Office Lens on Android, too. You'll have to wait until later in the fall to use the translation features, but the other additions are rolling out this week.