Ajua, you win a gold star! You quoted the email I received from HTC on the topic of who issues upgrades to HTC unlocked, unbranded phones. Soon after I received that email I also received a survey from HTC inquiring whether I was satisfied with customer service, to which I replied in the negative.
A few moments ago I received a phone call from HTC asking what it was that I was dissatisfied with. I replied that I had spent around $600 on an unlocked phone on the understanding (admittedly an assumption on my part) that I would receive future upgrades from HTC, not from my carrier (AT&T) -- and that had I known that to not be the case I might just as well have saved myself $400 and bought the phone for $199 on contract from AT&T.
I was then told that whichever rep responded to me was completely incorrect ("confused" was the word she used), and that as I had an unlocked, unbranded phone all updates to my phone would emanate directly from HTC. She apologized for the confusion and assured me that "clarifications will be made in the customer service area regarding upgrade policies for different types of phones."
I then asked the obvious question: So, when should I expect an upgrade from HTC? Unfortunately, I got the usual answer: "We'll tell you when we're ready." So on that score I don't know any more than I did before. But it is good to know that I will not be getting AT&T bloatware on my phone via a software "upgrade".
I would like to add as a long-time iPhone user that I could not be happier with my HTC One in every respect -- and I'll feel the same way even if I never see 4.2.2.