That's a very interesting thread and I guess that just a few of the OP's questions will be enough to start a flame war ;D. Nevertheless, I'll weigh in with my personnal opinions and views of things based on my experience.
1. Are 18 Megapixels enough?
Unless you plan on printing poster-sized formats, I think 18 MP is plenty enough. Of course, if cropping is part of your daily processing workflow (not my case), then more MP is certainly desirable to start with but this won't necessarily translate into a higher resolution of the end-product since the lens/sensor/dataprocessing have also to be factored in.
2. Why do we need more than 12 stops of DR?
to improve the rendition of the final images, especially at high iso (>6400) where there's definitely room for improvements.
3. What ISO setting will we need to take pictures on a new moon night?
with a tripod, 100 in enough. without a tripod, I'd like a clean 409600 or more please ;D
4. When will mirrorless camera take over?
Seeing the latest progress from Fuji and Sony (improved AF and EVF), my guess is that we'll see the tipping point within five years or less. My feeling is that the "biggest change in Canon's history" being rumored here and there is in fact a complete (fast or gradual) change of the company's DSLR's lineup into a mirrorless platform (DPAF sensor anyone?), possibly with new dedicated pro-grade lenses adapted to the new platform - a bit like what Fuji has been doing for the past two years with their X platform, except with a far less retro design, with FF sensors and with products adressing pro needs.
5. Assuming Sony, Nikon, or Fuji had the same lens selection as Canon, and money was no issue, would you switch? Why?
If canon does not come up with a good mirrorless platform (i.e. pro-grade equipment) before 2015, then I'll definitely make the switch to Fuji. I already ordered their X-T1 with a XF 10-24/4 OIS lens for evaluation. Color rendering, high ISO performances, image quality, JPEG engine and EVF specs look all really excellent on the various reviews out there, and this combo has only 68% of the weight of my 6D+17-40L (850g versus 1255g) while providing an even wider field of view (Fuji's APS-C has a crop factor of 1.5, giving a 135 FoV equivalent of 15-35mm for the XF10-24/4) and image stabilization.
My need for extreme ISO performances and paper-thin DoF is limited, so I don't have a problem going back to the APS-C format. This transition will also reduce considerably the weight and size of dedicated lenses, which is important for me as I like having my photo equiment at hand as often as possible while not compromizing on performances. Since the best camera is certainly the one you have at any given moment, and I am sure I'll have the Fuji at hand more often than my bulky Canon combo whenever an interesting scene presents itself, I thus sense that Fuji has a more interesting value proposition with their X system than Canon with their EF-S or EF-M.
Moreover, I don't do sport or BIF, so I have no need for a cutting-edge AF. I also see that Fuji has some really awesome XF primes, like the 56/1.2, and I really like their lens roadmap (see
here), which at least gives some perspectives for the future as opposed to Canon's opaque communication. What's more? Some of their lenses will be weather sealed (like the X-T1 body) and all XF have really excellent optical performance and mechanical constuction/finish, which cannot be said of all EF-S and EF-M lenses from canon. Finally, the EVF truely opens up a new world of flexibility compared to OVF (focus peeking, image rendition preview and live histogram...), especially for low-light and infrared works.
I think it is about time Canon step up their game in the mirrorless domain, and they do have the technology and R&D power to blow the competition out of the water if they wanted it, so there really is no excuse. If my experience with the X-T1 comes out positive and if I see that at Photokina Canon still puts most of its efforts and ressources on video-making mirrorslappers, then I'll start selling my L lenses (and eventually my 6D) to finance my gradual transition to Fuji's X platform. I think that I will end-up following this path anyway because Canon, being a large corporation (slow decision making process, choice for low-risk strategies) and already holding the #1 market spot, has no real incentive to push mirrorless innovation the way Fuji or Sony does...
6. Is IS necessary on wide angle lenses? Do you even use IS on your lenses?
I think so as this enables lower shutter speeds (for water smoothing or lower ISO setting) without having to carry a tripod around. And yes, I always use IS on lenses provided with this feature as I don't like carrying a tripod around.
7. What's better, USM or STM?
I don't do video, so I don't care.
8. Should DSLRs have video or is just a waste of R&D & money?
I see video as a nice, but not necessary addition to DSLR functionalities.
9. Is DxOMark THE authority on lens and sensor measurements?
In my view DxOMark is by no mean THE authority in lens/sensor measurements; their scoring system is way too unclear (to the point that I don't trust it) but I do like the possibility of comparing different lens+camera and sensor parameters.
, but everyone's posts are either well-thought-out or really funny! I think rs' comment about monitors and prints should be the final post in every DR discussion, though I have seen some monitors 
