There have always been jokes made about the archetypal SCOOBY-DOO characters, once adults who grew up with the shows came of age – such as Shaggy obviously being a stoner because he was unshaven, always hungry, and hears his dog talk. This also includes things that are now "facts" about the characters, that were only inferred in the shows (or even just "headcanoned" into existence), such as Freddy and Daphne being a couple, and Velma being a lesbian.
In fact, when James Gunn wrote the 2002 live-action SCOOBY-DOO film, he capitalized on those post-modern conceptions of the characters – Shaggy had a girlfriend named Mary Jane and is introduced "hot boxing" a van (which, to be fair, turns out to be him cooking), Fred and Daphne were canonically a couple, and Velma was gay. Except…that last one didn't make the final cut, as he explained recently on Twitter:
Unfortunately – as Gunn tweeted – the studio chipped away at Velma's LGBT representation until there wasn't even a hint of it left in the final cut (to the point where, again, she ended up with a boyfriend in the sequel). However, luckily her orientation was made canonically gay almost a decade later in the 2010 SCOOBY-DOO: MYSTERY INCORPORATED animated series, confirmed on Instagram by the series producer Tony Cervone:
Of course, that's just one canonical incarnation of a lesbian Velma (since Gunn's interpretation didn't get past the script stage), and it's doubtful the current SCOOB! incarnation will carry that portrayal forward (at least not explicitly) – but it's still an interesting factoid nonetheless. And unlike some modernization of characters, making Velma gay isn't really a contradiction at all, as romance was never explicitly shown in the original series whatsoever (even Freddy and Daphne's cis-het relationship is merely implied, and barely at that), and in my opinion it's always nice to have more visible representation, regardless.
Either way, Gunn's next film – THE SUICIDE SQUAD – is still scheduled for April 6th, 2021…but we'll keep you updated if there are any changes.