3.0.2 – This patch is released today. It marks the end of Burning Crusade content patches.
3.0.3 – I would expect 3.0.3 to be a relatively minor patch which updates many bugs and other problems that transitioning to 3.0.2 will create. I would not be surprised to see it released next week.
3.0.4 – Quite possibly 3.0.4 will be another bug fixing patch. I would suspect we'll see it shortly before Wrath of the Lich King goes live. So probably sometime before November 13th.
3.0.5 - While Wrath will no doubt be a solid product upon release, Blizzard will need to patch in some changes here and there. If there are two minor bug fixing patches prior to Wrath's release, 3.0.5 will be the patch that fixes bugs and maybe adds a little something immediately following its release.
3.1 – Confirmed to be the first major content patch for Wrath. Already done. Will include Ulduar 10-man and 25-man raids. Ground mounts will swim in the water instead of vanishing. Hopefully new dances will appear. Dual specs are also a very likely possibility for this patch.
3.1.1 – Chances are 3.1.1 will be a quick bug fix patch to correct issues that developed in 3.1 with Ulduar.
3.1.2 – Probably some more bug fixes and fine tuning of the new raids, perhaps other raids around the same difficulty of Ulduar to make things flow better.
3.2 – Confirmed to contain an unreleased and unknown raid instance.
3.3 – Confirmed to contain the Icecrown Citadel and finish the story of the Ashbringer.
3.4 – There were a whopping 12 major content patches prior the Burning Crusade line of patches. However since then there have been only 4 major patches. Blizzard seems to be taking an approach where they release a smaller number of larger patches. If this continues I doubt we'll see beyond four major content patches to Wrath of The Lich King, especially since we know 3.3 will contain the end of Wrath's main story line.
4.0 – This will be the patch branch for the expansion after Wrath of the Lich King. Many fans are expecting something such as the Emerald Dream, or something to do with the Maelstrom. Some are thinking WoW might branch out into other planets or realms in the Warcraft universe, which include Argus, K'aresh, and Xoroth.
4.0.1 – This will most likely be an incremental patch from the beta patch tree of 4.0.0, to the patch immediately before the release of the next expansion. We never really see a x.0.1 patch on the live realms, and it would be a safe bet we won't see one in the future.
Patch 3.1 brings us Ulduar, dual specs, significant changes to all the classes, and more! We've got you covered from top to bottom with our Guide to Patch 3.1.