While I might argue that KG's defensive presence makes him a top 20 player still, regardless of the fact, I can't see any team that'd really want him. If you're a bad team, he won't make you a contender by himself. If you're a mediocre team, you'd have to give up everything that makes you good to get him. And if you're a contender, you'd have to blow up the core to get him, and even then, the C's probably wouldn't want aging vets for him.
Maybe in a year when he becomes an expiring contract, but I don't see him going anywhere this season. And that's why I say we make another run at #18. Our trade situation, especially if we re-sign Ray to a 2 year deal, is going to be much, much better next summer.