Upload & Sell: On
I think the sweet spot hinges more on affordable memory and processing, coupled with processing speed. Today, around 25MP is the sweet spot if shooting an abundance of RAW, but in a couple years, possibly 50MP will be comparable.
At the moment, my computer is slightly behind the curve, and I only have a total of 3TB storage: one in the computer as C/D; one external F, one back-up G (plus a mothballed 320GB). I'm on the verge of buying another drive as both these externals are full.
We'll soon need 3TB in-computer if we are moving to a lot of 50MP images. Prices are coming down on computers and memory, while cameras are going up in in-camera processing and MP.
So, I'd say we are always at the "sweet spot" -- it's the resolution we can afford on broad playing field.
Otherwise, the sky is the limit for MP and resolution.