Gmail for Android gets a unified inbox view
Found on Ars Technica on Monday, 30 March 2015
The Official Gmail Blog just announced that, starting today, an “All Inboxes” option will show up in the Gmail for Android navigation drawer (presumably, this requires an app update). The new option will display all your incoming mail from all your accounts in a single list.
Third-party mail (Exchange, Outlook, Yahoo, etc.) stays on a third-party server, and Gmail on Android just downloads the mail to your device and displays it.
Wouldn't be too surprising if that changes in the future.