I can report this much, that my i7 quad core 2.93 GHz iMac with 16Gb RAM uptook the 36mp D800E files without much of a bother. There's probably a bit more churn going on in the background compared to my 16mp cams, but not so much that I notice any waiting. Right out of the gate I shot some 7-frame HDR sequences where I was combining 7 200mp+ TIFFs for a total of 1.5Gb per combined image, and it didn't seem bad at all. I also recently had a shoot where I batch processed about 200 images and Capture NX2 munched through them without any hiccups.
Yes my hard drives are full, but they already were full anyways and I'll just have to buy more. Especially with my latest foray into video exacerbating the situation. BTW, D5200 looks like a great video-rig too and over on the D600 forum we have just proven that one can adjust (D7000) Aperture on the fly during recording by shooting video in shutter priority and manipulating exposure compensation button (providing the much vaunted manual aperture control that some video shooters consider a minimum criteria).
So all in all, I was expecting a much worse processing hit from these new higher mp cameras, but it hasn't been bad at all for me. Can't speak for lesser machines, but at this level I have been just fine and that has been a very pleasant surprise. But you may be right if one was operating a barely tolerable machine on 10, 12, or 16mp images the jump to 24 may cause some pain