It's not a recent trend. Cutesy, too-adult kids have been in movies since before Shirley Temple and Margaret O'Brien.
What Spielberg should get kudos for is Henry Thomas (and the other child actors) in E.T., who were the first kids I remember seeing in a movie that looked and sounded like real kids.
I'm personally more ambivalent about Bale's character in Empire of the Sun. I think the script soft-pedaled some of the real creepiness in the Malkovich character, and that made Bale's admiration of him much less problematic. But I still think Bale did a phenomenal job with what he was given, and I'm a fan of the movie generally.