Update : HTC One A9 is official now
HTC One A9 that has also been rumored as HTC Aero or HTC Hero is a mid-range phone wrapped in metal body. HTC One A9 will go official on 20 October in in the event held by HTC. HTC has already issued a teaser image that you can see below.
According to the latest rumor HTC One A9 will be launched with Android 6.0 Marshmallow OS. So this will be the first HTC device to get Android 6.0. It will feature Snapdragon 620 SoC that makes it a mid-range smartphone, but Finger Print Sensor and metal body puts it above mid-range range device. So it may cost more than a usual mid-range device.
Technical Specifications of HTC One A9
HTC One A9 would feature a 5 inches display with 1920 X 1080 pixels resolution, Octa-core 64-bit Snapdragon 620 or 617 SoC, 2GB RAM, 2150 mAh battery, 13-megapixel rear camera with OIS and 4-megapixel front camera (Ultrapixel), Finger Print Sensor etc.. It will be available in various colors ; Gold, Space Gray, Black, Brown and Silver.
In terms of design, HTC One A9 looks like iPhone 6. HTC has given the same touch. Some of the images of HTC One A9 got leaked via Weibo that you can see here.