Henchoz hasn't stepped a foot wrong since he's been back in the team that i can remember so he hasnt given any reason to drop him. If someone plays well, they should keep their place in the team (see Derbyshire!)
I highly doubt that he will play a major part in the first team next season, but he has showed that he can be depended on when called into the team so he deserves this extension in my opinion. I
Its not like hughes signed him to be first choice, but injuries have dictated that he got his chance and he's grabbed it with both hands!