Like people have said, these third developers just see free cash for bigger titles on other systems. I don't see why they care so much, A high quality game will probably yeild more money then lolmoney games 3rd partys keep making.
Though honestly its not as bad as I think the artical says. Its not like 3rd party's only have cheep games. Besides if PS3 still has low sales (in comparison) I don see why more support wont be shifted.