The Japanese market is one of the few for which a reasonably reliable indicator of actual retail sales can be found (through BCN).
For several years there has been a strong trend in Japan, with mirrorless cameras slowly nibbling away at the overall interchangeable lens camera market. If you look at the 20 most popular interchangeable lens cameras sold in Japan, you get the following (totals don't add to 100% because this is only the top 20 models):
- 2009: DSLRs 75.5%, mirrorless 11.5%
- 2010: DSLRs 61.9%, mirrorless 23.2%
- 2011: DSLRs 55.2%, mirrorless 28.1%
Obviously, a clear trend. Of those mirrorless, m4/3 outsold Sony in the last two years pretty much 2:1. That makes a bit of sense, as there are two companies in m4/3 and only one Sony. Olympus tends to outsell Panasonic in the m4/3 crowd, but mostly because Olympus has been using price to unload older m4/3 cameras (the E-PL1 and E-PL2 were their biggest sellers, and none of the new models introduced mid-year cracked the top 20 in 2011). The most popular mirrorless camera in Japan for 2011 was the Panasonic GF2, the second most the Sony NEX-5.
I expect 2012 to be more telling, as the Nikon 1 rose to top 10 status in late 2011 and seems to be staying there. Needless to say, I expect the trend to continue and mirrorless to get closer to equal market share with DSLRs in Japan in 2012. The big question is whether 2012 will be the year that Canon decides to play in this game or not. That could make a major impact that increases the speed of change.
Meanwhile, in the latest CIPA numbers (cameras manufactured and shipped) I note that interchangeable lens cameras imported into the US fell to a smaller percentage overall than to Europe and Asia (that wasn't true of compact cameras). It's difficult to say why that might be, but it might be because mirrorless hasn't yet caught on in the US and thus those cameras are being diverted elsewhere. But it could also be other factors, such as a (wrong) guess that the US economy would not grow in 2011 coupled with lack of supply issues due to the quake in Japan and flooding in Thailand. For example, neither Nikon nor Sony had their expected inventory in DSLRs in the US for the last quarter of 2011 due to floods cutting off supply. 2011 was an odd year, to say the least.