Are you saying a white one is not as good as black. I thought they worked the same, it's all a matter of opinion about color. In a year you can't give either one away anyway.
Unless Olympus and Panasonic update their sensor this year, if they hold tight at 16mp I think these E-PM2s will hold value. Regardless of price the current Olympus camera line-up is quite mature image-wise and even the lowly E-PM2 can produce professional-caliber photos!
E-PM2 prices are so low that I don't think it's important whether it'll hold value or not. It's currently the best value in m43 lineup by a mile. I use E-PM2 and E-M10 and the IQ is indistinguishable. E-PM2 is great as a second body provided that your other camera uses same battery, e.g. E-M10
I can't imagine I need better sensor than what we currently have. Oly should spend their R&D on improving on-sensor PDAF and capturing sports photography market.
I'm of the opinion that any M43 camera with a current generation sensor that has already been discounted significantly from is intro price t'll hold it's value reasonably well until cameras with tangibly better sensors are available - unless it was well over-priced at it's intro like the E-P5.