The BMCC is a phenomenal camera, especially considering the price, no matter what anyone says. Also, despite being the first one to come out of the Blackmagic stables, it is still a seriously good camera.
IMO, though, I a not sure it is a DSLR killer. Well, for many reasons.
1. It weights a LOT more than the GH2, and even other DSLRs. Whereas the 5D Mark iii vs BMCC's dimensions and weight:
Dimensions: 152.0 x 116.4 x 76.4 mm vs 166.2 x 113.51 x 126.49mm
Weight: 950g (including battery and SD card) vs 1.7kgs (the battery is internal, non-removable).Thats almost Twice the weight of the
Mark iii. And almost 4 times the weight of the GH2 (it weighs 444gms, with the battery and SD card). The SSD Drives, I am guessing, with add a noticeable amount of weight, to the BMCC.
2. Most people who shot with the 5D and the GH2, would obviously be aware, of the inherent imitations in (actual) Dynamic range and score in coloring and grading. They don't care too much about it.
3. The 12 Bit Raw and 4-4-4 is more of an Alexa and RED killer. The DSLRs aren't even close to that pedigree. I believe, that even though RED pretended to be targeting Canon, it was actually more seriously, attempting to wean away customers, from the BMCC.
4. DSLRs video is more out of the box. And, if you use a certain kind of profile, which is reasonably flat, you could tweak the video, in post, a LITTLE.
5. Good quality Sound recording is as much a headache on DSLRs, as it is on DSLRs. You need good quality mics, for both, though, due to terrible on-board sound, and lack of monitoring in most DSLRs (except the the D800, Mark ii, GH3 etc), sound recorders like the Zoom H4n or pre-amps (if you don't wanna sync) JuicedLink, are a necessity. A lot of Guerilla shooter even use recordes like teh H1, and sync later. Probably even dub, later.
6. I feel, a lot of amateur shooters and semi-professional cameras are not interested in using Rails and Mat Boxes, and even Follow Focuses. Especially people (like me) who like the whole charm of gorilla shooting. I am guessing, that most BMCC users will add all these, to make the BMCC, shooting, as professional as possible.
7. There are DSLR shooters, who use crews of 20-50, with matt boxes, follow focuses, serious lighting (HMIs, Tungstens, Fresnels etc). The word, for describing this pedigree of idiots, hasn't been coined, yet. Especially, since the FS100, AF100, FS700, C300 have come into the scene.
8. The BMCC cannot be used as a crash cam/ action cam. The new Hero 3 seems to be pretty decent, though, it cannot really replace the GH2 or even the 5D. For multi-cam action sequences, DSLRs don't seem to have a replacement. Yet.
9. The D800 and 5D Mark ii hover around the BMCC price. If you can afford 3k, for a video camera, add another 3k to that, for the SSD cards, and the upgrade, to your edit set-up, and Voila !!!
10. The GH2 costs $700, and the 7D costs $1500. The T4i costs $800. If DSLR, is something, that one is looking, for, then, there are cheaper options, at a fraction of the cost of the BMCC (and the 5D Mark iii), for video. As videos have shown, saying that the 5D Mark iii or Mark ii some low light kings, is all bullshit, especially, if you cannot use that quality, for professional video. And, if it crushes details, at the cost of low light.
11. Since the Data Rate is reasonable, you don't need many TBs of storage. On the BMCC you need about 7GB of space, per minute of video, shot at 2.5k RAW. For other formats, there is a huge amount of compression, so, that should not be an issue. But, I am guessing, you wont be picking up the BMCC, if you wanna shoot 4-2-2 or 8 bit
12. Most DSLRs aren't too taxing on your system. You don't have to upgrade to 16GB RAMs (or more) and use Graphic Cards that cost as much as you entire computer, for editing DSLR video.
The 5D Mark iii and the D800 are as lousy, for video, as their 4 year old cousin, the Mark ii. All the extra features are just publicity gimmicks. It hasn't added much to the video quality. They haven't added more than 50-100 lines of resolution and the 4-2-0 codec is the same.
DSLRs and the BMCC were never in the same race, to begin with. The BMCC is a purebred greyhound, and the DSLR is a pekingese. There is no competition, between them. There never was.