Standards for IoT have been proposed by several disparate groups, but no single set has been internationally approved, tested and accepted. I doubt if there will ever be standards that address the requirements and responsibility for resetting a device for resale. It is not something that Manufacturers would deal with. It is more likely to be a Government imposed consumer protection edict rather than a standard - this usually happens after a few people get thoroughly burned or die. What about all that military stuff that will eventually hit the resale market. Besides despots, civilians can actually buy this stuff. In mid 2016, the US Military tested self driving tanks (the battle of the mechanical machines ===> alas, off topic). No doubt all military gear gets scrubbed down before being sold on, but all you need is just one to miss the neutering process.
