I think Heath would've won even if he was alive. Consider the other nominees in 2009:
* Josh Brolin in “Milk”
* Robert Downey Jr. in “Tropic Thunder”
* Philip Seymour Hoffman in “Doubt”
* Heath Ledger in “The Dark Knight”
* Michael Shannon in “Revolutionary Road”
Not that those nominees weren't deserving, of course. I've seen each of those films. Hans Landa/Chris Waltz is a tough performance though.
Trust my opinion, because I am a part of the official Academy Awards organization of judges. I am not just a forum poster who has an self proclaimed unlettered eye for judging acting skill.