My guess would be that 1 to 3% of the tunes that charted will be the ones to get through and the rest will mostly be forgotten about. By "getting through", I mean tunes taught in music history/appreciation programs as representative of the genres of their times, as well as those (tunes) frequently cited on one list or another.
That's what happens while the core audience is alive. It's why, although the Eagles had 12 songs that peaked at #12 or higher (and five number ones), you're unlikely to hear more than three on the radio now.
Chuck Klosterman is a writer who focuses on pop culture. He has a theory that eventually, Chuck Berry will come to stand for the entirety of the rock era in the same way that most people can only name John Philip Souza when it comes to marching band music (if they can name any at all).
Souza's first big hit, "The Washington Post March" was 1889, 136 years ago, so we'd need to be here in 2092 to know for sure about Chuck.
I think he'll be wrong-ish, if only because Elvis and The Beatles existed and (barring a nuclear war between the time I finish this sentence and then) so will their movies (in some form), but he's not that far off.
That would mean that The Rolling Stones and The Who and Led Zeppelin get lost in the sands of time, but consider this:
In 70 years since the pop-standard era began to give way to the rock era, we've already distilled the standards era to Frank Sinatra, Tony Bennett, and maybe Dean Martin and Sammy Davis Jr. (riding Frank's "Rat Pack" coattails, though Sammy had the talent and, until the drugs, the discipline to be a much better performer than Frank).
Ella Fitzgerald, I'd like to think, instantly commands respect and recognition, but I wouldn't bet big on that. Billie Holliday is more a legend passed down by word of mouth than an artist that most Americans alive today have heard even once.
Bing Crosby sold way more records than Frank. He's been marginalized as a Christmas artist, along with Perry Como, Nat Cole and Mel Torme'. And then there are several dozen others, big to huge in their time, that are already off the radar of all but the most serious listeners and students of the era.