In none of these examples is the implication given that you are playing a previous edition. There is either "Oh the newest" or "Which one?"
Then all you have done is proven your examples are wrong, or your experiences do not speak for the whole.
1. This is wrong because you incorrectly assume it would lead people to only hear of 4th edition. They would likely ask what D&D is, and unless from some WotC marketing personnel; be told a bit about the game in general, or explain that it is several different games of which only one is in production, but because that was a choice made by the company, and that many people acros the world still play all versions of it, and no proof can be made as to which version is more popular since they are not sold as competing products to find out.
2. There are MANY more responses to that one besides your hopeful binary ones. Other responses include, but are not limited to, and presented here solely for examples:
Not that WotC crap I hope.
If it is Mentzer then you should try Moldvay (vice versa)
I prefer the options given in AD&D.
3.5 screwed it all up, there was nothing wrong with 3.0!
2nd edition was not needed and ruined the game.
etc
3. The end result is correct, which right there proves the dilution exists and anyone of education would be able to clearly see it since there is not one immediate thought that comes to everyone's mind when "D&D" is mentioned as the option and oft times need to ask "which one" exists.
4. You forgot this all together. They know of the game and respond "I don't want to play a game where you play elves and fairies, I would rather play vampires or werewolves", as they walk away covered in glitter with their fake fangs.
Joking aside there, your presumptions that 4th edition is the default conclusion for anyone to think when saying "D&D" to them is proven wrong by yourself as you present cases where the dilution exists such that anyone could and would have to ask "which one?"