I exaggerate slightly. But not by much.
Since the World Cup is on at the moment, we can use football as an example. In case you're not familiar with the famous "Brazil/Zaire free kick incident" of 1974, watch this video:
At the time, it was widely believed that the player in question, Mwepu Ilunga, made this mistake because in Zairian football they didn't take free kicks as the "official rules" dictated. This story doesn't actually seem to be true: the player in question later said he did it hoping to get sent off, as a protest because he and his team mates weren't being paid properly by the Zairian footballing authorities. (There's also an apocryphal tale that gets bandied around holding that the Zairian players had been threatened with death by Mobuto Sese Soko if they lost the game by more than 3-0 and either the pressure got to Ilunga, or he was desperate to try to waste time and prevent the Brazilians scoring again.) But it illustrates a point: at that time, football was played quite differently in different parts of the world. It was rare for players to move overseas to play football, and there were radically different playing styles in England, Scotland, Italy, Brazil, and so on. It was only 20 years prior to the Ilunga free kick that Hungary had revolutionised international football by creating their new "WW" system and suddenly unleashing it on the unsuspecting English; it was possible for them to do this because nobody in England had a clue what was going on in Hungarian football. It was thus entirely possible for a viewing audience in 1974 to imagine that in Zaire they had different rules for free kicks: it's a reflection of how diverse the public understood international football to be.
It wouldn't be possible nowadays. Football has globalized, and as it has globalized it has homogenized. I sit here writing this blog entry watching Brazil v Switzerland. Most of the players on both teams play together or against each other regularly in English, Spanish, German or Italian club football. Their club teams and international teams use the same or very similar formations. The two sides both emphasise the same qualities in players. In 1974 a tie between Brazil and Switzerland would have showcased two very different styles. Now, they're basically the same.
The same will happen with D&D. It is happening now. When I was a kid, the only frames of reference you had for understanding what D&D was actually like were the people around you who introduced you to the game, the page long "example of play" in the PHB, what you could glean from various hints and asides in the text of the rules themselves, and maybe the little "choose your own adventure" style intro in Red Box Basic. That was it. Other than that, you were on your own: D&D was what you and your friends made of it.
Think of a new player nowadays. You can go online and watch Will Wheaton, or a thousand other people, actually play sessions of D&D right in front of your very eyes. You can read forums, blogs, and other online resources discussing different play styles in intricate detail. You can directly contact many RPG designers through social media. You can go on Tumblr or Twitter and heap abuse on people who don't conform to what you think D&D is about. The texture of your introduction to the game, as a neophyte, is utterly different to what it was in 1985.
D&D will become like football. It's not that all games will be the same, and it's not that there won't be innovations. It's that we'll end up with largely the same play styles dominating (some people will prefer "narrative" style games versus "OSR" style games, just like some football teams play a 4-2-3-1 versus a 3-4-3 or play an attacking game versus a counter-attacking style, but they will deploy those styles in homogenous ways) and there will be much, much, much less variety than there once was.
What happens when your touchstone for "what D&D is like" ends up being Will Wheaton and not, say, your friend's older brother and his mates (which was my introduction to the game)? A more significant question than can be dealt with in a blogpost, probably. Switzerland have just equalised and it's got interesting, so I'll leave it up to you to deal with in the comments.

