There are still quite a lot of sports card collectors/investors buying the older cards. A T206 Wagner PSA 3 sold late last year for $3.25 mil and just a couple months ago a 52 Mantle PSA 9 sold for around $5 mil. Just a couple blockbuster sales.
It's all about certain sports figures like Ruth, Mantle, Gretzky, Trout, Jordan, Lebron, Kobe will always fetch high sale prices and likely continue to go up in value. Yeah the newer modern cards are gaining a lot of value because of all the hoopla with serial numbered cards and colored refractors of star players today who are out there on television for the world to see. It creates a lot of excitement and buzz. Not to mention businesses that do sports card breaking, pretty much like gambling in hopes that the breaker pulls a high end card for the player or team you purchased. That business is booming and doing quite well.
So to sum, it's a mixed bag. People will collect vintage cards, some collect newer ones, and others collect both.