I'm sure that there are tools to take a part the nexus 7. which would lead to the back coming off. Will there be a white oem back for sell? or any other color.? i know there will be some bootleg chinese back covers. but i want a legit one.
There are no plans to release a OEM replacement rear cover in white. That was an IO exclusive design. There are cases in different colors coming but you will never see that design anywhere but a IO edition device.
I wouldn't say never. It's not like last year where the IO edition had the custom printing on the back. I can see it possibly coming out in 4-6 months.
As for replacement, here's an idea of what that would entail: Nexus 7 Teardown - iFixit
I think it's safe to say that no, won't happen.