If he can even give 15-20 mins a night I think he would be worth the investment, especially if Ray signs somewhere else. You can probably get him for like 3 mil a year. Give him a 2 year contract to expire with PP and KG (hopefully).
I know his knees are shot , but just last year he helped Portland single handily beat Dallas (the eventual champs) in a playoff game by going off in the 4th.
He obviously can't be counted on to defend guys like Lebron and Wade, but he is definitely a shot maker and a big game performer. Definitely wouldn't mind adding him for relatively cheap for at least next year.