The new Gmail is here, very slowly rolling out thanks to staged rollouts that may take a few weeks to complete. Thankfully, we already have the APK, and it's only a quick download away. The version number is 4.5-694836, and it's beautiful. Gogogo grab it!
Update: If you don't see the categories, go to the desktop version of Gmail, click the gear icon on the top right, and select Configure Inbox.