So, it is confirmed that the plastic version of HTC One M8 will be called as the HTC One E8. The yet unannounced device is listed on HTC China's website as HTC One E8. It was earlier rumoured to be named as HTC One M8 Ace and HTC One M8 Vogue Edition.
It will feature similar hardware internals as the original HTC One M8 but the metal body will be replaced with plastic, or say, polycarbonate. HTC has also replaced the 4MP UltraPixel Duo Camera with a regular 13 MP camera. It might be the same sensor which is used in the Desire 816.