According to @upleaks, it seems that the One M8i is based very closely on the HTC One M8 and could even offer up a similar design and to a certain extent, similar hardware features as well. However the main difference here is that the processor will be swapped out for a Qualcomm Snapdragon 615 chipset instead.
This is an octa-core chipset with four 1.7GHz cores and another four 1.0GHz cores. HTC is also expected to do away with the UltraPixel and will feature a 13MP rear-facing camera with an auxiliary 2MP, and a 5MP front-facing camera designed for selfies, but other than that the specs are said to be identical.
This includes a 5-inch Full HD display, 2GB of DDR3 RAM, BoomSound speakers, NFC, Bluetooth, and also a battery smaller than 3,000mAh. No word on when HTC will announce the handset, but like we said with MWC 2015 around the corner, perhaps we could learn more then so do check back with us during the event for the details.