HTC will indeed be calling the One (M8) successor as HTC One M9, yes without the parenthesis. The smartphone branding was confirmed via a sighting on the HTC Canada website, which we stumbled across while looking through the website pages. The webpage with HTC One M9 branding has since been removed, but you can still check it out in Google Cache (while it lasts).
In addition, the HTC Canada website has also revealed that the One M9 will carry the “One Life” tagline, not that it matters. Just for trivia purposes, the One (M8)’s tagline is “Beautifully Designed. Inside and Out.”
To remind you, HTC One M9 will be unveiled on March 1 in Barcelona at the Mobile World Congress and is expected to feature a 5-inch full HD display, Qualcomm Snapdragon 810 octa-core processor, 3GB of RAM, 20MP rear camera, Android 5.0 with Sense 7 and 32GB of internal storage with microSD card slot.