That's why I don't think we can just assume that Assange would draw the line at releasing something that would put lives in danger because of legal concern about himself. He is already in serious trouble, even without any evidence of his leaks killing someone. If the U.S. government wants to charge him with espionage, they do not have to prove that someone died from his leaks.
What about the fact that he clearly hasn't released anything that would put lives in danger? Lacking a specific motive not to do something hardly constitutes a motive to do something, and his previous record is pretty clean (on that front, although given the huge conspiracies to destroy him and his site I'm beginning to wonder if those allegations are just more of the same).
If the US government wants to charge him with espionage they'll have to prove he engaged in espionage, which they sort of can't.
Espionage, commonly known as spying, is the practice of secretly gathering information about a foreign government or a competing industry, with the purpose of placing one's own government or corporation at some strategic or financial advantage.
For a start, he never gathered any information, it was volunteered to him and he released it. If any espionage occurred, he's clean of it. And if that counts, they'll have to prove that releasing this information specifically benefits the state of Australia, which isn't engaged in any hostilities with the US or any other affected state that I'm aware of.
How, pray tell, can he be done for espionage?