Best Picture award is least predictable of tonight's gongs

Could this be the year for boldly going where no Oscar has gone before? On a night of potential firsts, James Cameron's Avatar has a shot at breaking one of Hollywood's longest-standing taboos and becoming the first science-fiction film to win Best Picture.

The 3D blockbuster, which, with box-office receipts of $2.5bn (£1.7bn), is easily the most lucrative film ever made, is gaining late ground on The Hurt Locker, and is now 11/8 second favourite to walk away with tonight's biggest prize. That would represent a victory for a genre which has for years been one of Hollywood's most reliable cash cows but has been prevented, perhaps for reasons of artistic snobbery, from winning a fair share of awards.

Only three sci-fi movies have even been nominated for Best Picture – ET, Star Wars and A Clockwork Orange – and all were pipped by unfancied rivals. But attitudes could be changing: The Lord of the Rings chalked up victory for the "fantasy" genre in 2004, while this year's shortlist also includes the alien invasion satire District 9. "It's a watershed year for science fiction," noted Cameron at this week's Visual Effects Society awards. "We've got two up for Best Picture. That's never happened before. It would be a real milestone if it did win because Star Wars was nominated but lost to a small film. ET, even though it was actually a small film, was nominated and didn't win either."

Whatever happens, Hollywood expects tonight's Oscars show, hosted by Steve Martin and Alec Baldwin, to be remembered for a selection of groundbreaking firsts. Kathryn Bigelow, the film-maker behind The Hurt Locker, is odds-on to become the first female Best Director over her fellow nominee and ex-husband Cameron. Also in the Best Director race, Lee Daniels is vying to become the first black winner.

In theory, the existence of heavy favourites in all the major acting categories makes this one of the most predictable Oscars of modern times. Jaws will hit the floor if anyone but Sandra Bullock, Jeff Bridges, Christoph Waltz and Mo'Nique collect the night's prizes.

However, a degree of uncertainty still revolves around changes to the event's format. For the first time in modern history, ten, rather than the usual five, films are up for Best Picture. A new preferential voting system is also being trialled for Best Picture. Instead of simply voting for their single favourite film, the Academy's 5,777 members have been asked to rank the 10 titles in order of preference. Some pundits believe this could see supporters of Avatar and The Hurt Locker deliberately ranking their rival at the bottom of the list, allowing an unfancied outsider such as Quentin Tarantino's Inglourious Basterds to sneak away with the award.

Confusion about voting rules is perhaps behind the fact that an unusually large number of Academy members – roughly 600 – waited until Tuesday, the final day of voting, to cast their ballot. That's also bad news for The Hurt Locker since last weekend it was involved in a scandal which resulted in one of its producers, Nicolas Chartier, being banned from the ceremony.

The final unusual element to this year's Oscars (by modern standards, at least) is that it is likely to be an underwhelming night for Britain. An Education is the least fancied of all the Best Picture contenders, with its writer Nick Hornby and star Carey Mulligan outsiders in their categories. Helen Mirren and Armando Iannucci, the UK's other high-profile nominees, are also considered long shots.