Xiaomi CEO Lei Jun answered questions from netizens in a Q&A session hosted by digi.ifeng.com. Many of the questions concerned the 4G edition of the Mi4. Leijun explained that the reason that the reason why the Mi4 that is out right now does not support 4G is not because they do not have the technology but that it is matter of releasing it at the right time. There have also been problems with the recently leaked black edition. Some say that there are problems with the paint peeling off. Lei Jun said that he was using the black edition and did not see any problems with the painting.
Xiaomi, which is still a pretty new company, has been made a lot of attempts on developing their products over the years. They even included NFC mode but due to very few users, it was scrapped. They have also implemented infrared mode which will hopefully receive a better response. [source]