I think Tim genuinely believes in his heart of hearts that Andy is better than he ever was. I honestly think he takes a genuine pride in what Andy has done and loves the potential for the future. At the end of last year I distinctly recall Tim saying he believes Andy will end up better than Djokovic. I think he can genuinely see that ability in Andy, which is very exciting.
I don't know about sour grapes, but Tim could probably have been jealous of Andy. I have often had a sense that Andrew Castle is, or has been, but I've never had that feeling from Tim. I get the feeling he feels he did all he could, but just couldn't quite win the big ones. It seems to me that he takes enormous pride in Andy and loves what he has done.
I think if Tim ever did feel twinges of jealousy when he realised Andy was the superior player and likely to have greater success, it would have been years ago and cancelled out by the realisation that the press had turned their attention towards the new star. It will have helped that Andy was always very respectful towards Henman and what he achieved and fully acknowledges his success helped to motivate him.
With Castle, I've always felt he's been full of admiration of Tim and Andy's talent and achievements. He is very up-front about his own abilities and career being inferior when talking about Andy and Tim and to the other more accomplished pundits, so if there is any jealousy from him, it's more wishful thinking, rather than trying to build himself up or bring anyone else down. Possibly also influenced by being a showbiz person, rather than a full-time sports pundit, so too much time listening to people who don't actually know what they are talking about, but I've never felt he was being mean. Wade on the other hand ...
I think as a pundit, it's hard to get it right. If you are too supportive, you get called gushing and flag waving. If you attempt caution, you can be accused of being negative. Tim has done a very good job of getting the balance right. He manages to steer clear of the punditry for punditry's sake type analysis, and is able to combine caution with optimism, which isn't easy.