i think no one cared about MP until nikon released the d800...Nope.
Some of us have been intrigued about the prospects of real high MP counts ever since Canon broke the news of their 50mp and 120mp prototype sensors, long before the D800 emerged.
Absolutely. The 120mp APS-H was probably one of the most intriguing pieces of news I heard from Canon the last couple years. (Its obviously a bit impractical right now, as few lenses can resolve 220lp/mm even at their best aperture (which is often lower than necessary to achieve that anyway), but its still intriguing to know its possible, and that producing something more realistic, such as a 47mp FF sensor, is within the realm of practical.)
So megapixels are largely for the cropping ability? How many people out there do this? I would think that unless you're shooting at 400mm to 600mm consistently, which would not be the majority of photographers, you could always just get a longer lens.
I currently shoot sRAW and have taken less than 50 clicks using the full raw on the 5D Mark II as opposed to over 100k clicks using sRAW. I personally would much rather have DR and other features than mpix. Mpix is probably close to last on priority list.
Beyond 400mm f/5.6, "longer"...or for that matter faster...generally means "to the tune of an ungodly price". The 300/2.8 L, 400/4 DO, 500/5 L, 600/4 L, even the 200-400/4 L all cost WAY beyond what the average or even somewhat above average person can afford most of the time (barring winning the lottery, hefty inheritance, literally struck gold, etc...you know, those kinds of things that happen to ordinary people every day.) So sure, you could always get a longer lens...if the lens itself is within reach
As for features, I'm in the camp that believes everything can be improved in a well-rounded way, rather than simply focusing on just one thing...such as just high ISO, or just more megapixels. We already have a 116lp/mm resolution 18mp APS-C sensor, and we know how well it performs with three-year old fabrication techniques and image processors. That is equivalent to a 47mp FF sensor, however a 47mp sensor released today that had exactly the same pixel pitch (density) as a three-year old 18mp APS-C sensor... It would have the benefit of three additional years of research into improving quantum efficiency, reducing read and thermal noise, improved manufacturing techniques that produce more effective microlensing, backlit rather than frontlit sensor fabrication, etc. etc.
Sure, I want better DR. I think we can get about two full stops of better DR, even on a 47mp FF sensor. I think we could have ISO 12800, possibly even ISO 25600 if you were willing to spend the money, along with a high 7-9fps frame rate, a decent AF system, AND better DR, all in one camera. Why? Well, the D800 performs pretty damn well on the DR and noise front for being a 36.3mp sensor, thanks to Sony Exmor technology which drastically lowers read noise (among other things). Because with an improved noise floor comes direct improvements in maximum ISO, by up to a stop. Improved quantum efficiency gained by say using a backlit sensor and/or improved microlensing would leave additional headroom, allowing for further gains on the maximum ISO front. I believe a 47mp full-frame sensor is possible because we already have numerous Canon cameras, from entry level to pro grade, using 18mp APS-C sensors that use the exact same pixel pitch, and (excluding low ISO read noise, which could be corrected at least by the Sony approach of embedding hyper parallelized ADC on-sensor) they perform extremely well.
I'd love to have ALL of that above right now, but I'd be happy to start with less than that and save myself some cache. Start with 32mp, maybe a stop improvement in DR, and one stop improvement to native high ISO (12800), coupled with a nice 61pt/21ct AF system, 100k RGB metering sensor, and I'll gladly spend $3500....in a heartbeat. I'd also gladly spend another $3500 three years down the road for that full 47mp, another extra stop in DR and maybe another extra stop of high ISO (and if thats not possible, well, we'll chalk it up to physical limitations, as that would most likely be why). I'd be quite comfortable with a 47mp, ISO 12800 (native), 61/21pt AF system that does at least 7fps for a LONG time. Even stuck with a 400mm lens, I'd at least have cropping power...and even the grand total of $7000 over three years is still half the $14000 price tag for a single, monstrous 600mm f/4 L series lens (something I wouldn't even consider myself fully qualified to use until I've had another several years of practice anyway.) (Do I think the price is too optimistic...maybe...but the D800 seems to be going for $3000, and its most of the way there already...so I don't think its unrealistic.)