This can be attributed to the slowly growing trend among Chinese smartphone vendors of refreshing the device's internals as frequently as possible to keep up with their high-profile counterparts.
Anyway, coming back to the OnePlus 3T, almost most of the specifications of the device have surfaced online (click here to read more about it) except for its launch date. However, a new rumour purported online which suggests a launch as early as November 14, 2016, at an event in London.
While the authenticity of the rumour is yet to be confirmed, it's most likely that the smartphone will be launched on the purported date given the fact that OnePlus is hosting a few Indians who got lucky during the company's Diwali Dash sale in London on the same date. Well, that explains all of it, right?
Additionally, other Chinese company's like Xiaomi and Meizu have already launched the updated versions of their current flagships meaning OnePlus has to speed up the launch before its other Chinese counterparts seize the company's share of the market. This could be another reason behind the earlier launch than anticipated.