The stars were on board, the contracts had been signed, and the third Guardians of the Galaxy movie was scheduled to begin shooting in early 2019.
But Disney's recent firing of director James Gunn has left the franchise somewhat up in the air.
The 52-year-old was let go after some distasteful jokes he made a decade ago (covering paedophilia, 9/11, the Holocaust and rape) resurfaced on Twitter.
But while the tweets may have been misjudged, members of the cast (along with 365,000 fans who have signed a petition) argued he shouldn't have been sacked.
"I will do what I'm legally obligated to do, but Guardians without James Gunn is not what I signed up for," tweeted Dave Bautista, who plays Drax, on Monday.
"It's also pretty nauseating to work for someone who'd empower a smear campaign by fascists #CyberNazis. That's just how I feel."
Over the weekend, co-star Kurt Russell added his voice to the defence of the director, telling Variety: "I do think we're getting a little too sensitive on maybe some of the wrong people."
"[Gunn] has a wonderful heart and a wonderful mind. I hope he is forgiven."
There's no doubt Gunn's original tweets were distasteful, and certainly intended to provoke. But, many argued, they were intended as jokes nonetheless.
"It's important to draw a line between ill-conceived jokes in poor taste and actual acts of paedophilia," wrote Screen Rant's Stephen M Colbert.
"By all accounts, Gunn has actually grown and changed significantly since he originally made the jokes, embracing the more family-friendly nature of his work with Marvel."
At the time of the tweets, Gunn was embarking on a career as a comedian - one whose jokes were actively intended to be edgy and politically incorrect.
He later drifted from stand-up comedy, going on to write and direct the first Guardians film, a huge hit for Marvel when it was released in 2014. A sequel, released last year, was also successful.
But, once his old tweets had been dredged up, several fans expressed outrage.
Disney was quick to sever ties with the director.
"The studio needed to act quickly," Karen Krizanovich, a reviewer and journalist who also works in the film industry, tells BBC News. "Whether firing was the best thing is questionable.
"The only thing that's certain is that all studios are on a steep learning curve."
Gunn had previously apologised for some of his misjudged tweets in 2012, but that was prior to the success of the Guardians franchise and so didn't attract much attention.
The recent rediscovery of the tweets, however, received much more publicity - and were difficult to overlook in the zero tolerance age we now see on social media.
After his sacking, the director issued an apology, saying he understood the business decision taken by Disney.
Given that Gunn had successfully directed two Guardians films prior to the tweets resurfacing, many argued, why should he now be banished from the franchise?
"It is very easy to react to any slight or misunderstanding without taking a breath to consider both actions and consequences," Krizanovich says.
"Hopefully we're working to a point where these cases will be fewer - or none - and what cases there are like this will be handled with more subtlety."
PR expert Mark Borkowski says there can often be ways for stars to return to their careers after a scandal - provided the situation is handled well.
"You disappear for a while, you look for help, you're contrite, and as long as the conduct doesn't return, you have an opportunity to re-gather your brand and look again," he explains.
"But I think what we're beginning to see are these peaks and outrages don't sustain. Because the audience move on very quickly to the next thing.
"If that person truly reflects odious views, there is no hope for them. But some people make mistakes in their youth when they're not really on top of what they're doing. They don't have the advice, they're not famous, and these things come back to haunt them."
He adds: "I do think there is generally a massive overreaction, and bad publicity doesn't seem to sustain... everybody has a way back."
That way back, however, is unlikely to come in the shape of him being rehired for the third Guardians film.
One person close to the matter told Variety: "I don't see Disney re-hiring him.
"Those tweets were so horrible and Disney has a different standard than other studios."
Krizanovich says: "Rehiring Gunn is unlikely as the studio is probably not going to want to be seen to be talked down."
"Film production is collaborative. Film crews are very tribal so the fact that the actors are standing by the director isn't surprising.
"Ideally some middle ground could be reached. Either way, it is great exposure - negative or positive - for the next film."