Xiaomi has scheduled to have a global launch of a new flagship smartphone on 15th of September 2017. This is not their first dual camera flagship smartphone introduced, the Mi6 was the first by the company to feature dual-camera with flagship spec.
There was speculation of the recently announced Xiaomi Mi 5X but it only powered by a mid-range SoC, the Qualcomm Snapdragon 625.
Our guess it could be the Mi Note 2 successor where it has been launched for almost a year now so it could be the Mi Note 3.
There was teaser released this morning and there will be more till the actual announcement.