Well, first off, let's not forget that Pepper asked Tony to shut off Happy's life support, because she couldn't do it herself.

Also, Tony placed his fate in the hands of Don Blake, not Thor. While Thor's honor might have prevented him from harming a man in a coma, Don's Hippocratic Oath absolutely would have, which, to me, indicate's a possible will to live.

Though it is also possible that he was allowing Thor (and the others) to be his judge, jury and executioner. Honestly, it is the twisted sort of way Tony might try to make it up to people.