An overview of Diablo 3 update features soon to be detailed by Blizzard is currently available on Battle.net.
According to community manager Bashiok, the Diablo 3 developers are in the process of preparing a number of developer blogs with information on what users can expect in Patch 1.0.4. These include:
"System Changes, by Wyatt Cheng
Senior Technical Game Designer Wyatt Cheng is preparing a high-level summary of some of the system changes planned for 1.0.4.
Legendary Item Improvements, by Andrew Chambers
Senior Game Designer Andrew Chambers is working on a blog detailing all the ways we're making Legendary items stand out.
Magic Find Update, by Jay Wilson
Following up on earlier discussions, Game Director Jay Wilson will be providing an update on how Magic Find is evolving in patch 1.0.4.
Class Changes, by Wyatt Cheng
Wyatt will also be providing a preview of the changes we'll be making for each class in 1.0.4 (and the philosophy behind those changes).
Patch Notes, by Lylirra
Of course, this is all building up to the actual patch 1.0.4 release, and we'll be releasing the full patch notes shortly before the update goes live."
Blizzard is yet to announce a release date for the long-awaited patch, however new information is promised to arrive in the "not-too-distant future"