I'm pretty confident Bonzi will stay. It looks like most teams that planned on spending their money have done so, so the only choices left are take the MLE from a good team and probably come off the bench or take the Kings offer and get to be a major part of a good team (whose got quite a fanbase for you now too). With Ben Wallace leaving Detroit and how they fell apart in the post season, benching for Detroit is looking a lot less interesting. Denver could still really use him, but he would have to squeeze in with the egos of Melo and Kenyon Martin (if they can't move him... which they probably can't because his contract in crazy and he is a drama bomb himself). I think the Kings can offer Bonzi a touch above the MLE, something like his last contract, and it would be a fair offer and a good place for him to stay.
That said, I don't think Kings fans would be totally crushed if he left. Kevin Martin is panning out really well and making him the team's true starter could prove to be a great thing. I'd hate to lose a talent like Bonzi, but I would be excited to watch Martin play.