HTC game plan: HTC One refresh in 2013, M8 sequel in 2014
The M8 is expected to be powered by a faster processor (Qualcomm Snapdragon 800?) and will have a larger screen sized in-between the 4.7 inches on the HTC One and the 5 inches seen on the HTC DROID DNA. You might remember that the HTC One was originally called the M7 which is why the sequel is being called the M8 for now.
So that is the plan, at least for now. A refresh version of the HTC One with minor changes, and a more impressive HTC One 2 "M8" for next year. It is not written in stone, according to the tipster, which means that HTC could decide to go in a different direction.