Oh, I'm absolutely certain of that, but I think that has almost certainly been true of every edition compared to the one before it. Admittedly, I wasn't around for the transition between the original game and 2nd Edition, so I'm not sure what that transition was like.
I've been around (from the outside looking in, admittedly) for the transition from (O)D&D (original) to BD&D (Basic) and 1E D&D (Advanced) as well as the transition from 1E D&D to 2E D&D. I've been a regular at conventions through those times and it is my feeling that 1E and Basic saw a lot of expansion including many younger players joining in the fun. I wouldn't characterize what I saw with 2E as skewing younger, though without hard numbers or any clues that could have been had if there had been a vobrant Internet, I'd say it is difficult to say. I think 1E probably skewed older than Basic and that Basic kept their crowd while 2E maybe drew some new players but mostly canabalized from 1E, those who felt 2E addressed problems they saw with 1E.
I think it is perfectly reasonable for many folks to feel that 4E isn't their cup of tea. I find questions of whether it is 'tabletop roleplaying as we know it' to be downright silly, myself.
People can make a lot of claims about what each edition did and did not manage to present but as someone who was a wargamer before there even were RPGs (and who still is alongside my RPGing), as someone who plays many wargames and RPGs, year in and year out for forty years, I can certainly understand what people are saying when they express that 4E isn't the same tabletop RPGing experience they had 12, 20, 30, and even 35 years ago. You might think it is silly, because it doesn't fit your own experience, but it is very much at issue for many, many people nonetheless.
The fact of the matter is that 4E is very much a ruleset that focuses far more on tabletop miniatures combat than any other edition ever has, and this is coming from someone who has played them all with multiple groups, in home games and at gamedays and at conventions for the last four decades. I've heard those who wish to defend 4E as a tabletop RPG and I don't doubt that their individual games might be very much about RPGing with limited use of the rules for tabletop miniatures combat. But, it's been very clear through all of the pre-release previews and through the design blogs and from the ruleset itself that 4E was meant to and does have a combat miniatures focus. This doesn't make it a bad game but it does make it very different from the tabletop RPG experience that past editions of D&D engendered. 3.XE moved it in that direction and 4E picked up the ball and ran with it. To deny that opens someone to questions about how much they really wish to have a meaningful discussion about the course of D&D design over its brand lifetime.
The arguments about this being dumbed down or that being about someone's attention span don't fly with me, so leave me out of those debates. I'm a fan of all sorts of games for their own merits, those that require quick decisions and near-realtime reactions even with complex rules and those that have simple rules where players can sit and debate for hours over minute decisions if that is the group's personal prerogative. Some games are designed well to do one or the other and other games fail to do either well. As far as I am concerned, all versions of D&D have been well designed in their time, cutting edge, and the hyperbole over the quality of the players in one camp or another is all hogwash. There's a spectrum in all camps of gamers, from casual players to those who are expert. D&D rulesets (all editions) have always managed to be welcoming to all skill levels of players, IMO, and those distinctions are beyond the purview of what I personally would like my corner of this discussion to include.
Most of the people on each side are likely more similar than they think - they just happened to prefer different games for different reasons, and that's that.
And in that we seem to agree, as you can clearly see from what I have posted.
