Olympus and Panasonic announced joint development of technologies and devices for the "Micro Four Thirds System standard," a new standard that extends the benefits of the Four Thirds System standard for interchangeable lens type digital camera systems by enabling dramatic reductions in size and weight.
When compared to the Four Thirds System standard, the primary distinguishing characteristics of the Micro Four Thirds System standard are: 1) Approximately 50% shorter flangeback distance (mount-to-sensor distance)
2) 6mm smaller lens mount outer diameter
3) Electrical contacts in mount increased from 9 to 11

The Micro Four Thirds System enables users to enjoy the high image quality benefits of the Four Thirds System's 4/3-type image sensor in a much more compact camera body, and also take advantage of significantly more compact lenses, particularly in the wide-angle and high-power zoom range. The Four Thirds System offers compact, lightweight performance, and the new Micro Four Thirds System will take this even further by making it possible to develop ultra-compact interchangeable lens type digital camera systems unlike anything seen before. The new Micro Four Thirds System also incorporates a greater number of lens-mount electrical contacts, enabling support for new features and increased system functionality in the future. In addition, users will be able to mount their existing Four Thirds System lenses on Micro Four Thirds System bodies via an adapter.

When new small DSLR cameras based on the Micro Four Thirds System Standard will be released is not clear yet.
More details in this press-release. Via PhotographyBlog.