I can tell you now that the MI2 will not be available until October, it states that on the website and the little button which relates to it is not functional yet.
When it is then this is how it will work. You will first have to register then you will have to work pretty hard as the phones will be sold in batches on a first come first serve basis, just like the MI1 was. How do I know this? Take a look at the evidence. They did that with the MI1 and if you go to the MI1S section on Xiaomi's site you can already register to enter the first two rounds of sale. It states that stocks are limited and just like last time if you failed to get one but registered then you will have to wait until they have another round of sales.
ANYONE WHO WANTS A MI One S EARLY HAD BETTER GET THEIR SKATES ON AND GET CLICKING!!!!!!!!!!!!!!!!!!
When we bought our MI1's we got our IT guy to spend two days clicking on the buy button which was often inaccessible due to volume. Eventually we managed to get hold of two phones but had to change IP address, mailing address and payment details to do it as Xiaomi also impose a one phone per client rule too.
Why they choose to do it this way I dunno. To make it seem much more exclusive, because they have a supply problem, because they are trying to limit traders from getting their hands on too many units and selling them at elevated prices? Those are a few of the different reasons I have heard thrown around here in China and the last one was given to me by someone from the service center in my city.
As far as buying a few and then selling them on is concerned, for now at least will be a problem for anyone. It's going to be a struggle to get one unit for yourself in China let alone several. Once it becomes more easily available here I think it will be the same everywhere.