Profiles will be broken down into 5 main tabs: Feed, Wall, Info, Photos, and “Boxes”. The feed tab appears to contain the News Feed as we know it, except with three new size standards: one line, short, and full.
There’s also a bit of confusion between this Feed tab and the new Wall one. Apparently users will be able to post items to friends’ Feed tabs (and their own) using a new Publisher tool. This is described as meant to replace the old wall attachments feature, so it appears as though the Wall will revert to plain text posts and no longer allow for rich media. But it will also incorporate all mini-feed items somehow.
Some suggest that the new Publisher feature will allow for FriendFeed-like conversations through comments, but the official documentation doesn’t make any reference to such capabilities. Screen shots showing comments appear to be only wall-to-wall conversations.
The “Boxes” tab will be where all the current application profile boxes are quarantined, er, showcased. While 5 tabs will show by default, users will be able to add their own tabs that display canvas-like pages for their favorite apps. This appears to be a trade-off Facebook is imposing on developers: isolate their profile boxes in a “boxes” tab but compensate them by allowing for more prominent, full-view pages. That said, Facebook will also be allowing up to 5 app boxes to show up across all tabs in the left-hand column (but they’ll have a severe height restriction).
Unfortunately Facebook has yet to release any screenshots of the new design except for the rather uninformative one above.
More information at Inside Facebook.