On January 27, Microsoft announced Office Online documents stored in Box, Citrix ShareFile, Dropbox and Egnyte get the same real-time co-authoring capabilities that Office Online documents stored in Microsoft's own OneDrive and SharePoint Online currently have.
Microsoft also is allowing more third-party cloud-storage partners to integrate directly with Office for iOS. Microsoft already enabled iOS and Android Office integration with OneDrive and Dropbox, which allowed users to access, edit and share Dropbox files from its Office apps.
The first of these other third parties to support this Office for iOS integration is Box, which is available today. Citrix ShareFile, Edmodo and Egnyte are "coming soon."
Microsoft also is promising that users who have been migrated to the new Outlook.com will be able to attach files directly from Dropbox, Box and OneDrive directly from inside their inboxes. They can send these files as traditional attachments or as cloud-based links. This integration will happen "in the coming weeks," but again only for those on the new Outlook.com.
Microsoft announced plans to migrate its existing Outlook.com users to the updated Outlook.com experience last year. But still many of us have not been migrated at this point. Microsoft officials told me late last year the migration to the new Outlook.com would continue into this year. I've asked if there's a projected end date for the migration. So far, no word back.