HTC says 1 + 4.1 = 4.2.2, not 4.3.
According to a recent tweet by @LlabTooFeR, the HTC One will be upgradable to Android Jelly Bean 4.2.2 quite soon. The tweeter in question is a HTC developer and described by GottaBeMobile as a "notorious insider" (would that be notoriously bad or good?). HTC has not not yet confirmed whether the One will receive the 4.2.2 update yet.
If HTC is to go ahead with this plan, it would mean that One users would finally have an OS on their phone that isn't nearing a year in age. However, with rumours flying around that Android 4.3 is on the horizon, it would be a strange for HTC not to wait for the brand new mobile operating system from Google. Then again, non-Nexus users are used to being a bit behind when it come to updates, so maybe it's not that strange after all.