Micron today announced an advancement in their DDR3 lineup today, with the introduction of new components that are much more dense than existing technologies. Using a 78nm-process, their new units will use 2Gb modules that provide for single sticks up to 16GB in size for servers and up to 4GB in size for desktops:

By using 2Gb components, Micron can enable 8 gigabyte (GB) and 16GB modules for servers and 4GB modules for desktop and notebook PCs, which are the industry's highest density DDR3 modules available.
With the advent of 64-bit processors and new programs (read: games) that demand ever-more vast amounts of RAM, it sounds very appealing to be able to snag a mere two sticks of RAM and have 8GB to roam with on a desktop. The modules keep the same standard 1.5V DDR3 voltage, carrying with it the same power reduction compared to DDR2 modules.

They don't mention when the modules will be available, but likely they will use their Crucial brand-name to divy it out once they are ready. You can read the full press release in the comments section.