As mentioned there is nothing that indicates how DSLRs are performing. First you don't even know how DSLRs are tracked - if they're considered part of "digital cameras". And even if they are you cannot make a determination as to how successful DSLRs are. If you think for a minute Sony cares about photographers so much they'll continue investing $$ in something that doesn't have a strong profit margin - forget it. Remember, with a large multi-faceted corporation it isn't even enough for an area to make a profit. It is also a matter of whether the executives believe another area could be even more profitable if it had the money going into DSLRs or full frame cameras.
Now, I'm not saying things are bad. Just that there isn't enough information available to guess whether Sony's DSLRs are doing well - and, more specifically given recent rumors - whether their full frame DSLRs are doing well enough to warrant continued investment. Those figures will never really be public knowledge. The best we can do is wait for world wide sales figures (not just Japan) to be compared in the DSLR realm. Or wait to see what new bodies are released.
I generally agree with the above but want to point out that gauging Sony's success in FF cameras by sales today is not completely fair, as the relevant models (A900/850) have been on the market for a while. Generally speaking, the longer a product is on the market its sales tend to decline (with some exceptions like the Nikon D90 which remains a top seller, at least in Japan).
Sony really has no current (new) products for higher-level users, having discontinued the A700 (now three years old) with no replacement, and having the two-year old A900 and the A850, which while only about a year old is virtually identical to the A900 except in shooting speed, and thus is two-year old technology. But, it's even worse, as the A900 is a "sister" camera to the A700 in virtually all its operating systems except for the larger sensor and a slightly modified AF module, so one could argue they A900/850 really are at least three-year old technology.
Then you have some of Sony's entry level cameras, like the new A290/390, which really are warmed over replacements of the 230/330/380, which were warmed over replacements of the 200/300/350 with much worse body designs. As the review of the A390 on this site points out, it has basically the same image quality and features as the A350 from two camera generations ago. Thus, old technology that has not been improved.
It appears that Sony is on the verge of coming out with a slew of new products, the first of which were the NEX cameras. Hopefully these new products will offer improved functionality, features and performance and will be far more attractive products to consumers. Hopefully at least one of those cameras will be the A7xx (I would not expect an A900 replacement until next year some time, assuming it comes).
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Mark Van Bergh
http://www.markvanbergh.com 
