There is word that DC is considering this, supposedly as a raise on Marvel's "Guardians of the Galaxy."

Is There Any Way To Do Justice To The Legion Of Superheroes In A Movie?

The claim is that Legion of Superheroes hasn't gotten an official greenlight yet, but that it is in "serious development" and is intended to be much lighter in tone to the rest of the DC movies we've seen so far.

...The dark, grim, gritty, asphalt-like nature of DC's recent spate of movies is a constant and common complaint. It makes total sense for the studio to branch out, both as a reaction to that perception and as a reaction to Guardians, which itself has been meme-ified into "Marvel can do anything."

... Legion of Superheroes is not exactly a direct analogue to Guardians. And DC is not a direct analogue to Marvel. Yes, a tree and a talking raccoon are out-there aspects. But the film takes place contemporaneously with the rest of the Marvel universe, which had already featured two movies about Norse gods faffing about in space. They started tying Guardians into everything with Thanos and the Collector showing up in earlier movies. And the McGuffin was part of the set of McGuffins that had shown up before.

Guardians was based around the easily-explained idea of "space misfits." How does DC, with its resolutely modern Earth-bound list of projects find a way into the idea of "it's the 30th century and there are a billion alien planets and all these aliens with superpowers live in a clubhouse together?" ...This seems like an unnecessary uphill battle that Warner Bros. is setting for itself.
I'm inclined to see this as a bad idea. I like LSH, but not only hasn't DC built a strong story framework to easily plug this into, but the cast of LSH is *huge*. I mean, this is a league that seems to have 15-30 members in it. Maybe more. It's like Star Trek -- there's a "League of Planets" with a zillion worlds. It just seems crazy to imagine throwing that into a single movie, cold.

It would be much better, if they want to do a "quirky team movie," to do a spinoff on the Justice League (from earth) as their go-to group (like "Justice League Europe" from some years back). I'm not sure of the JL roster, but I remember a lot of funny stuff with that group when Geffen did it, 20 years ago. Blue Beetle, Booster Gold, the Martian Manhunter, Guy Gardner.

Instead it seems like they have taken an ultra-serious/grit route and are going to do the main JL movie with Supes, Batman, Wonder Woman, etc. and make it dark. So why not the "spinoff" JL, with the quirkier heroes? That book was hilarious at the time, it was kind of like the "Loser Squad" with a really grumpy Batman trying to act as nursemaid/custodian.

It's not like Marvel hasn't had something similar -- there was a West Coast Avenues (more serious) + Bryne's spoofy "Great Lakes Avengers" containing heroes who were just horribly funny and kind of lame... but that's what made them funny.