Scooby-Doo is one of those stories that has become so much a part of popular culture that it has been endlessly reinterpreted in a relatively short period of time. The characters were born in an animated series in the 1960s and since then we've seen multiple animated reboots, a live-action movie, and a new animated film. These have all kept the core elements more or less the same, but James Gunn, who wrote the 2002 live-action film and its sequel, recently confirmed he wanted to make one significant change in his movie, Velma was going to be gay.
The idea of the character of Velma Dinkley being gay is one of those fan theories that has taken hold over the years along with the concept of Shaggy being a stoner and Fred and Daphne hooking up off-screen. These ideas were never specifically stated in the slapstick cartoon for kids, but there was anecdotal evidence that seemed to support them, and there's little evidence to discount the ideas entirely. James Gunn recently stated on Twitter that in his original script for the live-action movie, Velma's sexuality was going to go from subtext to actual text.
James Gunn has spoken before about the ways that his Scooby-Doo movie went through multiple iterations in pre-production. He's mentioned that one version of the script included a kiss between Velma, played in the film by Linda Cardinelli, and Daphne, played by Sarah Michelle Geller. While it's at least theoretically possible that the kiss could exist in the story without outright claiming the characters were gay, it seems that in Velma's case that was exactly the situation.
While Gunn has expressed some frustration at the way the movie was changed, he's also clearly been very happy with the way the movie has been embraced by fans over the years. If anything the live-action Scooby-Doo films are as popular or more popular now than they were when they were new. If the films had gotten more restricted ratings, as they would have under the original script, that might not be the case. Still, the edgier version of Scooby-Doo is such an interesting idea that it's not hard to want to see see what it would have looked like.
James Gunn's comments follow on those of Tony Cervone, producer of the 2010-2013 Scooby series Scooby-Doo Mystery Incorporated who, in an Instagram post, confirmed that, in that version of the animated series at least, Velma was also totally gay, and if you didn't pick up on that, you weren't paying attention.
Perhaps there will be other chances for different takes on the material in the future. We just got another Scooby-Doo movie with Scoob! so clearly the franchise is still popular. Anything is possible given enough time.