Well, he obviously does care enough about Chewie to want him and Leia taken to his ship. He's probably much more valuable alive (for his information about the Alliance) than dead.

And, just because he placed value on the droids in his past (just like he placed value on the lives of his human companions) doesn't mean he'd have the same value on them when he became evil. Like I said, he even turned on the humans closest to him, so him caring about droids... it just doesn't seem like it would happen.