Gmail will have tabs very very soon. The tabs will represent the new auto-sorting powers of Gmail has been granted in an attempt to make your email more useful.
It's an evolution of the spam blocker.
Google will be able to take notifications from services like Facebook (FB) and Twitter and file them away in a folder titled Social. Groupon (GRPN) deals and the never-ending onslaught of email from Fab will be tucked away in the Promotions folders. All those bills, receipts, and nagging reminders you don't really want to deal with? Updates folder.
And for those who still use message boards and mailing lists, there's a folder for any emails from that corner of the internet.