The obvious has happened. Writely and Google Spreadsheets have merged and the new products is named, not Google Office, but Google Docs & Spreadsheets. The strange name will probably be modified, as Google Docs & Spreadsheets & Presentations is just not a catchy name.
The good news for those who hated Writely's interface is that the unified interface is similar to Google Spreadsheets'.
Also now you can let collaborators invite other people. "The people whom you've invited can now add other collaborators to that spreadsheet. You can decide whether you want this capability turned on for each spreadsheet individually - the default for new spreadsheets is to allow collaborators to add other collaborators."
The next logical move would be to add a new web application for presentations and to integrate all these applications with Gmail, Google Calendar and Picasa Web, so they can share attachments, photos and documents. Some pieces of the puzzle are still missing, but Google can't deny they don't want to build Google Office.