Originally posted by PePe For APS-C 24 MP is quite sufficient at the moment. Also for me :-)
However, to get even close to the same pixel density for FF you would need a lot more MPīs, actually more than 36 MP.
At the same technology, #MP should scale with 1/crop^2. However, larger sensor sizes seem to bump their MP at bigger steps, meaning their #MP moves forth and back between like 1/crop^0 (read, is the same) and 1/crop^2 wrt to the next smaller sensor size. I found that heuristically, it is safe to assume #MP to scale like 1/crop on average.
This means that 14, 18, 24, 36, 60 MP are balanced resolutions for 1", m43, APSC, FF, MF(54x40) with a moderate advantage wrt reach for the smaller format, and a moderate advantage wrt image quality for the bigger format (with differences both smaller than a comparison by crop factor alone would suggest).
The next step will be a "resolution shift down" with 24MP for m43, 36MP for APSC, 55/60MP for FF and 80-100MP for MF.
Seems like a shift is due about every 3 years or so, with 2012 marking the current state. This would make 2015 the year for 55MP FF and 36MP APSC.
Of course, it won't last forever. I see a point of vanishing return around 100 MP for FF. Assuming a slow down of pixel count increases, this would make 2020 the year where this point is reached (60 MP APSC, 100MP FF). With probably no significant increase in pixel counts afterwards. And an emphasis on preprocessed downsampled raw output.
I may be totally off track. Its just my 2 cts, my current best guess.