When it was first announced, many fans assumed that David Ayer's Suicide Squad movie would be another "dark" addition to the DC Extended Universe - what with the "black ops team of supervillain murderers" premise and the word "Suicide" right there in the title. The precedent for DCEU superhero films to be "dark" was established by Man of Steel and further emphasized by Batman V Superman: Dawn of Justice, the latter of which even has an R-rated director's cut that will be made available for viewing on home release.
Currently, Suicide Squad is reported to be undergoing some (fairly expensive) reshoots, as most big-budget tentpoles inevitably do. However, one of the main intentions behind these reshoots is reportedly to lighten the film's tone and incorporate more humor into the mix.
The story (posted by BMD editor in chief Devin Faraci with information from unnamed sources) puts the dollar amount that Warner Bros is spending to beef up the film's fun quotient at around "tens of millions of dollars," and notes that the reshoots are apparently not a direct reaction to the negative critical reception of Batman V Superman's tone. Rather, the changes were decided on when audiences reacted with overwhelming positivity to an early trailer for the film which juxtaposed the violent onscreen action with Queen's "Bohemian Rhapsody" and heavily featured the Squad members cracking jokes and engaging in witty banter. According to Faraci's sources, that trailer did not match the actual tone of the film as it existed at the time - to the extent that the handful of gags on display may have represented "every joke in the movie."
However, BMD's repots indicates that these changes don't necessarily involve stuffing the film with extra jokes or transforming it into a full-blown comedy, but rather "beefing up fun character moments and interactions." If so, it makes a lot of sense. The so-called "Queen trailer" was cut to lean heavily on the idea that we're not simply seeing a succession of oddball villains but a cohesive team with its own bizarre chemistry, and ensemble films often live or die based on the kind of chemistry and unique interplay that can grow between the characters. Suicide Squad has already been compared to Marvel's Guardians of the Galaxy, which built most of its runtime around finding new ways for the personalities of its disparate crew to bounce off one another in funny ways.
Suicide Squad's actual plot has yet to be revealed, other than that it shares the same setup as its DC Comics counterpart of a covert U.S. Military agency offering pardons to incarcerated supervillains (Deadshot, Harley Quinn, Killer Croc, Katana, El Diablo, Slipknot, and Captain Boomerang) if they'll agree to put their special abilities to work as part of a black ops paramilitary mission with a low chance of survival. It's known that Jared Leto's Joker figure into the plot as well, while the film's trailers have featured sequences of the Squad seemingly engaged in battle with what may be monsters created by Enchantress (Cara Delevingne).
While news that the film may be less abjectly grim than originally anticipated will likely be received as something of a relief to many fans (and to those who appreciate comments like James Wan's claim that Aquaman will be "fun", signaling that not all upcoming DCEU films will be "dark superhero movies"), such rumors may also draw backlash from those fans who like the so-called "Snyderverse" darkness of Batman V Superman and feel it should be applied to historically violent characters like Joker and Quinn. Time will tell whether Suicide Squad ends up being any "lighter" (for better or worse), but it's worth noting that Suicide Squad was already set to be the first directorial effort by hard-action specialist Ayer (End of Watch, Fury) to not carry an R-rating.
Batman V Superman: Dawn of Justice is now playing in theaters. Suicide Squad will debut on August 5th, 2016 followed by Wonder Woman on June 23rd, 2017; Justice League Part One on November 17th, 2017; The Flash on March 16th, 2018; Aquaman on July 27th, 2018; Shazam on April 5th, 2019; Justice League Part Two on June 14th, 2019; Cyborg on April 3rd, 2020; and Green Lantern Corps. on June 19th, 2020.