According to HTC ROM developer LlabTooFeR (known for providing accurate info in the past), the One M10, aka HTC Perfume, is expected to have three internal memory options, depending on market: 16 GB, 32 GB, and 64 GB. We assume that the US will get the 32 GB and 64 GB variants, while the 16 GB model is made for emerging markets.
HTC itself didn't reveal much about the upcoming handset, though it did suggest that this is going to be a powerful device - probably thanks to Qualcomm's Snapdragon 820 processor. A MediaTek-based variant of the handset may also exist (again, this should be market dependable).
At launch, the HTC One M10 should run Android Marshmallow with the yet-to-be-announced Sense 8.0 UI on top. Other rumored features include a 12 MP rear camera (which will try to challenge the 12 MP rear camera of Samsung's Galaxy S7), fingerprint scanner, and 4 GB of RAM. It's said that the One M10 will only hit the market in May. At the moment, though, we can't confirm any of this.
The HTC One M10 is coming soon