That was just a discussion thread... and now some people think that just because it can run on 512MB RAM they can install it on their phones straight away... If kitkat ever comes to the Arc/S it will take a while for it to become stable enough for daily use. Also, the drivers we use are old since there have been no updates. If you guys want kitkat running successfully on this device, these old drivers need to be integrated with the new software, which is very tedious. Mike is already going to drown under 4.2 and 4.3, adding another OS to the pile will place him under more stress.
Don't assume the work we developers do is simple, just because an update came out that meets the system specifications means it can run just by downloading and installing it in recovery. If you ever tried to create a ROM by yourself, you'll find out that a lot of work needs to be done, along with many user complains and flooding your development thread with useless posts. That's how messed up the user community is nowadays. Jader's UHD ROM thread is one example of how users interact with the developer.