In a way, Captain America: The Winter Soldier was its own mini-Avengers movie. It was the most connected film out of Phase 2 of the Marvel Cinematic Universe and it serves as a bridge between the first Avengers and next summer’s followup, Age of Ultron. It also had Steve Rogers (Chris Evans) forming and leading his own team in a story that helped introduce several other new key characters from Marvel Comics.

Of course there was The Winter Soldier a.k.a. Bucky Barnes himself (Sebastian Stan) who was re-introduced into the modern era, but it was characters like Falcon (Anthony Mackie) and Agent 13 (Emily VanCamp) whose introductions help expand the Marvel Cinematic Universe beyond the super-powered heroes. When it comes to origin stories though, the most interesting new character we see develop and literally transform by the end of the film is Brock Rumlow (Frank Grillo). Spoilers ahead.

When Grillo was cast as Rumlow, fans of Marvel Comics knew it could be leading to something big. Rumlow is known as the villain Crossbones in the books and he’s a key player in many Captain America stories, having crossed paths with plenty of other big name villains and heroes. He’s visually distinguishable by a dark mask and outfit with crossbones on it and – as showcaed in The Winter Soldier – he’s an elite mercenary trained in many forms of combat.

Frank Grillo as Brock Rumlow

At the end of the Captain America sequel we see him wheeled down a hospital corridor, severely burned but clearly alive. Like most talent joining the Marvel Studios family, Grillo signed a multi-picture deal and he will be back. Even when we chatted with Captain America 1-3 co-writer Christopher Markus on the set of Cap 2, he hinted at a potentially dark (i.e. R-rated) future for the character.

“I would say he’s learning to be Crossbones in a way. With Frank Grillo, he’s a great actor. When he wants to, he can turn on this light that makes you think, “He’s out of his mind,” and I think somewhere down the line he will push past the R rating. He doesn’t in this movie, mainly because it’s PG-13, what are we going to do past an R? We can’t go past the PG-13. Taste of things to come? I don’t know if I’m leaking…”

Fast forward to present and Grillo was a memorable and entertaining part of the Captain America sequel – but that’s only the beginning of what we’ll see of Brock Rumlow as he returns for Captain America 3 which begins shooting next year for a May 2016 release. Grillo told Collider earlier this week that he’s “cautiously optimistic” that moviegoers will see him in “the not too distant future in the next installment of Captain America.”

“Very early on the Russos said, ‘Look, this is an origin film for this character. We’re gonna discover who this is and this is a big movie with a lot of moving parts, but we’re gonna discover you in this film and, you know, here’s the information about who Brock Rumlow turns into and blah, blah, blah.’ And so we’ve had multiple discussions about what comes after that, that thing. So, you know, it’s obvious Rumlow is covered in rubble and burned to crisp at the end, but you see he’s still there. They don’t do that for no reason.”

And of course, directors Anthony and Joe Russo are already working away on Captain America 3 where they will return to direct off a script by Marvel Studios and Captain America regulars Christopher Markus and Stephen McFeely.

NEXT PAGE: Grillo Talks Crossbones Costume & Other Appearances >

And for his trademark costume, Grillo cannot officially confirm what his appearance will be as Rumlow 2.0 but he can sure hint.

“He needs a costume! Coincidentally it could be a mask with a crossbones on it.”

Keeping on the costume front, Grillo tells ScreenCrush a similar story – while again trying his best to maintain secrecy while failing to hide his excitement at continuing his part of the franchise.

“Yeah, his face is burned. If you read the comics about Crossbones, you know, Marvel always takes their interpretation of the comics. It’s exciting.”

What’s even more interesting is that Crossbones can show up in other properties as well, as a potentially reoccurring villain in the shared cinematic universe.

“No. He could show up in anything. He could have his own thing. He could really have his own thing.”

And that shared universe extends beyond the two theatrical releases annually. Crossbones has crossed paths with Daredevil in the comics and that’s the first of the four Marvel Netflix series in development and begins shooting this year. Excited to see Grillo have a bigger role in the MCU? Is Marvel actually considering an R-rated project? Would that open the doors to characters like Punisher and Blade fitting into the franchise?

More: Anthony Mackie Talks Captain America 3

Guardians of the Galaxy opens August 1, 2014The Avengers: Age of Ultron on May 1, 2015, Ant-Man on July 17, 2015, Captain America 3 on May 6 2016, and unannounced films for July 8 2016 and May 5 2017.

Follow Rob on Twitter @rob_keyes for your Marvel movie and TV news!

Sources: Collider, ScreenCrush