Well, clearly you know more about it than me. But your rules of advertising apply to the general economy. I rather suspect that the rules of practice are different when your product is competing almost solely with your own discontinued product, the product in question never expires so no one strictly requires a new version, and the primary improvements of the new version are better usability.Instead, you say "We changed x" and tell people what that means for them. As the song goes, "You've got to aaaaaaac-cent-U-ate the positive!" You don't bring up potential negatives. YOU don't do it. You let Joe Customer find out the negatives by himself, or wait for your competitors to point it out.
Personally, I suspect that people's interpretation of the marketing was colored by preexisting preferences, not the other way around.
Just look at this thread- its being regularly claimed that 4e's marketing upset "people who liked 3e."
Obviously that's a silly thing to say. We all know its a silly thing to say. You know it, I know it, we all know it. People who liked 3e are almost certainly the primary purchasers of 4e! They just like 4e more, or like to play the current supported edition of the game, or any number of reasons.
But people are tribalistic and want to claim ownership and throw out those they don't like. So they declare themselves to be "the people who like 3e" and imply that people who like 4e aren't.
The reality was that the editions were actually being compared, and consumers were actually being exhorted to choose one over the other. I'm not sure that WotC could have made everyone think that wasn't true by changing their language, especially given the emotional reaction people were inevitably going to have to an edition shift, and the resulting colored perceptions.