I have suspected for months that the 4/3 (and mFT) systems will be huge. Finally we have a system that takes great photos, has interchangeable lenses, and is much more compact than DSLR's (both bodies and lenses). Here is the link to an article from dpreview about the growing popularity of 4/3. For these reasons I believe this system will replace DSLR's as the most popular system for a majority of shooters who recently stepped up to DSLR's and those thinking of upgrading. Have you noticed how many people are carrying DSLR's now? Of course DSLR systems can be expected to remain the camera of choice for most pros and for amateurs who are very demanding, but there are many more "casual" shooters who still want to take good pics and for whom the small sensor P&S will not do. For the latter group, it will be 4/3.
For a little more background, I shot some with a Minolta film SLR, then began to get much more active when I bought the first Canon Rebel. From there I have used many DSLR's including 20D, 5D, 1Dmk2, 5D2 and Sony A900. I even used Contax 645 MF for a while; wow, wow, wow great stuff but soooo too big. I finally got tired of these big rigs and sold them all. I now have a GF1, and also a Leica M9. Sometimes I'm not sure which I like more, but I do like them both and do not miss shlepping the bigger cameras and lenses. I do miss what the medium format can do, but too expensive and just too much.
Anyway, size DOES matter!