Ten.

The year where I'm assuming "Nine" will win Best Picture at the Oscars brings us a hell of a shocker by AMPAS.
Their Best Picture lineup, which has contained five nominees and remained that way since 1943, will expand starting next year to ten!
AMPAS Presidnet Sid Ganis stated:
"After more than six decades, the Academy is returning to some of its earlier roots, when a wider field competed for the top award of the year,” said Ganis. “The final outcome, of course, will be the same – one Best Picture winner – but the race to the finish line will feature 10, not just five, great movies from 2009.”"
He apparently just saw "Happy-Go-Lucky" and is filled with unreasonable optimism or he has, like most people alive today, lost notion of historic sense and rationality.
Has he forgotten that a wider ballot won't mean voters acquire better taste? Because as much as we can end with a Best Picure lineup like the one from 1939 (I wouldn't know which one to kick out) or something out of the blue like a documentary being nominated in the top race (after all it was back in 1938, in a decennial lineup, when we had our first Foreign Language film nominated for Best Picture), we also could find ourselves with ten "Crash"es, "Frost/Nixon"s and "Ray"s.
We'll see how it all turns out, for now I can't believe that "Up" will be a Best Picture nominee! That makes this whole thing almost seem good!