The current crop of m4/3 sensors are fully capable of fulfilling 95% of professional needs and 98% of amateur needs. But in the current very competitive marketplace, to stay competitive m4/3 needs higher resolution. Thus a resolution increase is only marginally related to improving image quality--its primarily a business necessity. I fully expect to see Oly increasing resolution by the next Christmas buying season.
I agree it's a business necessity given Olympus Imaging's continued poor financial performance (see p. 53 in their 2014 Annual Report):
http://www.olympus-global.com/en/ar2014/pdf/ar2014e_14.pdf
Sony has seen their 24MP APS-C and FF sensored cameras continue to gain mirrorless market share, and Samsung has just won DPR's Gold Award with an unusually high 87% rating for the 28 MP BSI APS-C sensored NX1. As Ben mentioned earlier, it's the high performing 1" 20MP BSI sensors showing up in what should be downmarket cameras from mFT that put PanOly's continued use of non-BSI 16 MP sensors in a glaring light.
Like it or not, the reality is a great many people looking to buy an ILC rate MP's high on their list, almost as if they equate it with horsepower in a sports car. For PanOly to continue to linger at 16 MP non-BSI sensors is simply very out of step with the market.
Why do I stay with mFT? IBIS and the nice range of quality yet affordable small and light lenses, plain and simple. What has me considering a used E-M1 over an E-M5 II? 30% less cost and better tracking thanks to the latest FW update.
What would have me buying a new Olympus camera? Improved AF tracking across the board combined with a 20+ MP BSI mFT sensor that clearly outperforms the current 16 MP sensor and, more importantly to me, allows for significant cropping of my photos of birds and wildlife without a penalty in resolution. Combine this with the 300mm f4 and Olympus could have the dream set-up for a compact mFT camera/lens combination for wildlife.
My concern is that, given their continued financial bleeding, Olympus Imaging may simply not have been able to afford a new sensor for the E-M5II, thus their resorting to styling and a gimmick that allows them to mention the word 40 MP under their breath for advertising purposes.
I pray they're not in such straits, but should they wait a year or more to introduce a current design sensor in an E-M1 II, I have concerns. Market misses like the E-P5 and E-PL7, and snark hunts like the Air, don't lessen this concern.
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Sailin' Steve