As the deadline for voting in the Academy Awards approaches this week, Tinseltown's elite could yet make movie history. If British director Steve McQueen's 12 Years a Slave is named best picture, it will be the first time a black director's film has taken the top Oscar.

Cheryl Boone Isaacs, who will preside over the ceremony on 2 March as the Academy of Motion Picture Arts and Science's first black president, has already hailed 12 Years as a potential game-changer for black film-makers, and one that may begin to loosen the stranglehold that white, mainly male executives have over the industry. "I would say that means a major door will have been kicked down," Boone Isaacs said.

"I believe very strongly that the entertainment and motion picture business is going to be more open and aware of different voices."

Yet there are concerns that cinema's racial barriers remain in place despite what has been hailed as a milestone year for black film-makers. Several key performances and movies have been pushed out of the running for Oscars this year and Hollywood history has shown that previous awards have done little to alter ethnic profiles.

There is no denying that success for McQueen's film will make an impact. It has been critically lauded both for its unflinching portrayal of Solomon Northup's ordeal at the hands of sadistic plantation owners and for tackling themes of slavery that Hollywood has long been accused of glossing over.

The film has 14 Oscar nominations, including best actor for Chiwetel Ejiofor and Lupita Nyong'o, the female lead, as well as one for the screenplay, by African American writer John Ridley. McQueen's film underperformed at last month's Golden Globes, often seen as an Oscar bellwether. But for Boone Isaacs, a former publicity chief at Paramount Pictures, it has already helped make 2013 the best year for diversity in cinema "in the last decade or so" thanks to "quite a few films that give us a different voice, a more diverse voice".

While some of these, including a remarkable supporting role performance for Somalia-born actor Barkhad Abdi alongside Tom Hanks in piracy drama Captain Phillips, have been recognised by Academy Award nominations, other acclaimed black film-making productions are notably absent.

The Butler, a weighty historical drama charting the life of a black domestic worker in the White House that stars Forest Whitaker and Oprah Winfrey, has been shut out of the Oscars, despite a raft of awards and nominations elsewhere – including a Bafta nod for Winfrey.

There is also resignation among many industry observers that success for 12 Years will represent not so much a breakthrough as a blip – token recognition for a film that many believed worthy of accolade even though they found it difficult to watch.

Djimon Hounsou, a Benin-born actor whose two Oscar-nominated roles include a performance alongside Leonardo DiCaprio in the film Blood Diamond, in 2007, responded with weary resignation when accosted by a journalist hunting for upbeat quotes about the film's award potential.

"Why is it every time you get one black actor or two black actors, you talk about 'this year is the black that, or the black this'. Come on, man!" he said, half-heartedly trying to avoid the camera. Asked if this could be black film-making's biggest year, he was equally dismissive. "It might, but then again, you hand it to one and it feels like 2014 was 'The Black Year'."

He may have a point. Sidney Poitier became the first African American to win best actor at the 1964 Academy Awards for Lilies of the Field. That was hailed as a breakthrough, but it would take nearly four decades for Denzel Washington to repeat the success in the film Training Day in 2001.

Similarly, Kathryn Bigelow's 2010 win for Hurt Locker, hailed as a landmark for sexual equality, has yet to be repeated by another female director.

Observers say Hollywood's glacial pace of change is down to a self-perpetuating cycle fuelled by commercial interests. "It's such a high-risk industry," Darnell Hunt, an academic who has studied diversity in the entertainment sector, told the LA Biz website. "And the people making the hiring decisions tend to be risk-averse. They want to hire people similar to ones who've succeeded in the past, and those are white males."