This is a translation of an article from Portugese site Occlumencia - so please excuse any minor errors:
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In 2010, the "gaffe" committed by Warner Bros to cancel the 3D conversion of Harry Potter and the Deathly Hallows Part 1 was subjected to criticism by James Cameron, director of the two most successful films in movie history, Titanic and Avatar, who found the cancellation a complete "blunder".
[Now he has attacked the finale once more] in German newspaper Der Spiegel:
"Hollywood is out of ideas..... [They] created a second part to a successful film simply because they knew what sort of reception it would get on release. These excesses are getting ridiculous."
Titanic and Avatar together earned more than $4.2 billion while they were in theaters.... [Although] Avatar was released - and re-released - in 3D, no Harry Potter movie has so far been converted to the format."