Garett Rogers reports that Google prepares a new version of Gmail, according to a message from the translation console. It's not clear what are the new features, but one thing that will change is the user interface.
When Google introduced Gmail in 2004, it was one of the first important web applications that used AJAX, but not in an excessive manner. Meanwhile, Yahoo and Microsoft released new versions of their mail services that tried to duplicate the familiar interface of a desktop mail client like Outlook (Yahoo bought Oddpost - an AJAX pioneer, while Microsoft rewrote Hotmail from the ground up). Yahoo Mail Beta had many problems with performance and that's why the classic version of Yahoo Mail is still available as an option. Windows Live Hotmail offers by default a classic version that doesn't use AJAX because the new interface "was too slow to load, too different and, well, just not like the old Hotmail it was intended to replace". The advantages of a desktop-like interface are many: an easier way to move a message to a folder using drag & drop, a reading pane that lets you read messages, "infinite scrolling" for reading your mail, but the trade-off is an interface that reacts very slowly and is not user-friendly.
The new Gmail interface could add some new views for your messages, a way to group related messages, sorting messages by size or sender and improve the search by indexing attachments and providing a better way to filter search results.
Beyond the interface, Gmail 2.0 could be an important part of the new social trend at Google and may even become Social Gmail. Google could use your messages to detect social relations that would the base of a new contact management application. Because you use Gmail's address book in an increasingly number of Google applications to share web pages, photos, documents, blog posts, Google could show you a comprehensive overview of all the items shared with a contact.
Many people asked for a Google Reader integration in Gmail (you can already do that using a Greasemonkey script) and a recently leaked video mentioned this possibility, even though Google Reader still has problems with scaling and wouldn't handle Gmail's traffic.
Gmail should also add offline support using Google Gears. "Gmail Offline will allow users to browse, reply, save drafts and do everything that currently Gmail does in an offline mode even when you don't have an Internet connection," reported an Indian newspaper. More likely, the offline Gmail will provide limited access to some of your recent messages, to your contact list and will let you compose new messages. It's just a small compromise for those who don't want to use a desktop mail client, but need offline access for their mail and contacts.
The IMAP support would make Gmail an even better option for the enterprise, so Google might also consider complement POP3 with a more robust and flexible protocol.
Hopefully, Gmail 2.0 will continue to focus on simplicity and user-friendliness, while polishing the interface and adding new features that connect it with other Google applications. One of the goals for Gmail 2.0 is "70% user happiness", so don't expect it to be perfect.
Update (October 30): Gmail 2.0, now available.