First off lets look at the facts.
On certain cars, the sound is being rendered differently from GT5, with examples such as the Red Bull X series, they sound imho a step up from GT5 in GT6, there is also the Lexus IS F which sounds better now, the Z4 M is near it, they have that german engine scream present in AMG vehicles and high marque BMW's but its not there yet. What can not be disputed is that the engine sound overall has IMPROVED maybe by not much, maybe by a small margin, or even 1% but it is a definite improvement. The way the sound is generated is singular on one end. What I mean is that it seems to be more or less a pure exhaust note on certain cars, and on others, it is engine noise. Good car sounds do a mixture of both exhaust and engine noise, as IRL to produce a recognizable and coherent sound. Here is evidence to back up my claim, the Stingray '14 with a stock exhaust, when you listen to it, it has that "whoosh" sound like having the windows down, and that to me is more of an exhaust note, even though the sound itself doesn't sound close to a real life Stingray. Then there is the C63 AMG and SLS AMG, you can hear the pure engine note of particularly recognizable AMG whine, but the exhaust note, the rumble of the massive V8s in those cars are absent. Sound systems may confuse, but if you truly take time to look and listen, you can tell that the sound channel is singular.
Then now lets look at the assumptions and claims
PD and Kaz has stated sound may be patched in a later update. Now I've looked at the news, the interviews, the press releases, but the word MAY is a big one here. That is no guarantee. The word may, like maybe is just a 50/50, a shallow promise with no real meaning. I'm optimistic so I'm hoping they do it, but we must remember that Kaz and PD never went out and stated in their exact words that ," Yes, we will patch GT6's sounds in a future update" all they said was the sound engine wouldn't make the release date and they hope to maybe patch it. Now what I think is that hopefully due to pressure from the community and its consumers, and maybe even car companies tired of being portrayed inaccurately ingame will make PD incorporate the sound engine.
Now lets agree to disagree.
We all disagree that honestly, GT6s sounds are good. Yes, I said it, its not good maybe to a man born in the middle of the ocean who has never heard a car, but overall they aren't good. This doesn't contradict how I said it has improved, it just means that it went from worse to bad, but that doesn't mean it becomes good, its still bad, its just a step up from worse. What I think is that we should simply let time be a judge. Let PD do their job, they are working nonstop, as consumers, we often look for faults in the product over the pros first, and even if the pros heavily outweigh the cons, we will endlessly gripe about the one fault we find. We already bought the game, lets just sit and wait and lets see what PD can do. Game companies don't take a day off on a launch title, they are endlessly working on getting more content and fixing issues.
Just my thoughts