1. I never talked about this when the D3x was released.
No one ever really talked about the D3x, the Sony A900 had the same sensor for a third of the price, and the 5D2 was the hot topic with live view and video. I personally know two photographers who dumped their MF/LF film kits over the 5D2.
2. I am saying that that it will be remove one justification, if the Dynamic range is there. The logic is pretty straightforward: Can people justify MF? of course they can[1]. but they will have one justification less.
Pretty big shoes to fill, seeing as it's Canon after all, it needs to be able to match the Nikon D8xx series let alone the 645 systems.
3. MF use to have far more dynamic range and resolution than DSLRs in the olden days. Later, MF no longer had a dynamic range advantage (MF vendors were able to keep some people unaware, until the CMOS sensor was released), now DSLR are matching resolution.
In the olden days, the only factor was film size, as every camera had every type of film available to it. With digital, small sensors are faster and easier to design, produce and sell, while larger sizes need proven technology that can produce a good enough yield for the required dimensions, resulting in them getting stuck with decades old base technology, like if development on CRT displays continued to this day. The Sony 33x44mm sensor is the very first medium format sensor that's actually based on the same modern technological base as smaller cameras, and is a good indicator of how things would have been if large-size CMOS wasn't prohibitive to manufacture.
"Matching resolution" is a pretty bold statement if you're only counting pixels - the 36mp D800 in some ways had let down many early adopters who discovered that Nikon glass is woefully inadequate to resolve the sensor, and began adapting other brands...
4. I agree that, if medium format keeps an advantage on image quality, the current developments will help MF grow. Amateurs and even some professionals will want to differentiate themselves from the mirror-less commodities.
In my opinion, MF needs to, and may well soon go mirrorless too.. and I don't mean tech cams, just regular cameras with autofocus. If Sony has any sense about them, and they continue developing large sensors, it may no longer be that MF will have to make do with old tech.
5. Because of volume,MF sensors are likely not to represent the last technology for long. The strength of medium format is the size of the sensor[2]. 48 x 36 mm is the point were size become a very strong advantage, enough to compensate for a generation delay on technology.
All it's going to take is a relatively inexpensive MF camera, like a big Sony mirrorless, to introduce more people to the concept and it's going to snowball from there. The ice will get broken sooner or later.
6. When the new CMOS sensor was released I did the same commentary, the sensor should be bigger. I also stated that the next generation DSLR will match or surpass the resolution of the Sonny sensor, and say that it will complicate marketing. So I am not reacting to another high pixel DSLR, I am showing what I was talking about when the sensor was introduced.
I'm happy there's a Sony Exmor 33x44mm sensor in the first place, never mind size. Sony says it's difficult to manufacture as it is, so give it time, maybe give them money too. I would much rather have 51 million pixels that are over 5 microns big each.
7. If it's real and has the proper dynamic range the sensor on the Canon will be about 8660 x 5770 pixels vs 8280 x 6208 for the IQ250. Most people don't shoot Otus lenses, so the IQ should prevail. As I say is one justification less.
As I said, using proper DR and Canon in the same sentence is dicey given their history, but the problem of resolution is also one of file size. Do I really want to shoot the 5D R knowing i'm using up 60mb+ each time for detail I may not even get? People who will buy this camera will almost certainly be those who have TS-Es, Otuses, and the new Sigma Art lenses and have been waiting for so long for something just like this.