The problem is not the phone, it's the company.
While the One maybe an awesome phone, as an HTC Desire HD owner, there is no way I'd ever buy another HTC product. The company no longer seems to care about supporting devices once they are in the hands of the consumer.
HTC actually isn't too terrible with regards to updates. Most phones are getting at least one update (The One X went from 4.0.4 to 4.1 and is getting a sense 5 update in the future)
The real problem is that people are buying phones expecting updates past what is promised by the manufacturers. In the dumbphone days, you bought a phone and it had the same software version its entire life.
The approach consumers should be taking is "Do I want this phone for 2-3 years if it were to stay on the version of software it ships with". If the answer is no, the only real safe bet is a phone like the Nexus 4 which Google will personally deliver updates to, regardless of carriers. Carriers slow down the update process by adding their own qualifications an update needs to meet.
It takes effort to update an entire line of phones and companies are going to focus on what makes them the most money.
In terms of updates for flagship devices, HTC seems to be second to Samsung, but better than all others (many of whom still on 4.0 or just recently got 4.1). As for lesser devices, I read that overall HTC seems to be the most punctual, but no company seems to care about updating lesser devices on time.
But you are right, with flagship devices, they are starting to fall behind more and more. They used to be even faster than Samsung, now they're usually a month or 2 behind. Then again, you can't expect the company to work at 100% efficiency when they're losing so much money and are trying to cut costs.
As for 4.2 on this phone, I haven't tried one myself, but there are plenty of custom 4.2.2 ROMS (Jellytime being one of the more popular ones) than run very well on this device. Without some official drivers from HTC though, there always seems to be one or 2 things that don't quite work 100% (like Bluetooth and camera).
My opinion still stands. HTC does a horrible job of supporting their phones. Until they prove they are willing to support devices for the full 2-3 years that consumers will have them, my recommendation would be to buy a Nexus device or possibly a Samsung. I know my next phone will be one of those 2.