The movie has had very little dropoff in attendence
Avatar will likely have a long run in the theaters and must make about 80% of the box office it has already made in 17 days.
The 3D Imax showings are still mostly selling out.
Its daily and weekly grosses are holding up better than Dark Knight. So minimally Avatar should make 50% more in the USA. It is unlikely to have Titanic's level of of repeat viewings although 50% seeing it two or three times for the spectacle is possible. Titanic at 17 days only had made 25% of its eventual total box office.
A final US box office of $540-750 million seems reachable. Foreign box office of $1.4 to 2.1 billion looks reachable.
So $1.85-1.95 billion in total box office and possibly over $2 billion if there was a rerelease at the end of the year or in 2011 with a strong showing or if Avatar has anything approaching the "legs" of Titanic. If there is little dropoff in boxoffice over the next 2-3 weeks that will indicate a likely over $2 billion haul.
The highest percentage of total box office being international box office were for some 2009 big movies (2012 and Ice Age: Dawn of the Dinosaurs at 77-78%). Big movies with strong visual appeal appear to have moved up from 66% foreign box office.
If Avatar has $600 million in domestic box office and matched Ice Age: Dawn of the Dinosaurs foreign/total box office ratio, then Avatar would have $2.05 billion in foreign box office.
NY Times estimates that Avatar cost about $500 million to make. The financing has multiple sources.
Published reports have put the production budget at more than $230 million. But the price tag would be higher if the financial contribution of Mr. Cameron and others were included. When global marketing expenses are added, “Avatar” may cost its various backers $500 million.