A character will die in Avengers Age of Ultron. Based of upcoming movies we know that Iron Man, Captain America and Thor will not. In my opinion this is the likeliness of the the remaining characters to die.
9 and 10.) The Vision and Scarlet Witch
I do not believe at all that they will die.
8.)War Machine
The loss of Tony's best friend at the hand of his creation would impact his story in Avengers 2. However I believe that War Machine will part of the "New" Avengers rumored to be lead by Captain America in "Captain America: Civil War."
7.)Erik Selvig
His role will probably be minor in "Age of Ultron." I think its more likely that they would want him to return for "Thor: Ragnarok" also. If he does die it is unlikely that his death would be the main death of the movie.
5 and 6.) Nick Fury and Maria Hill
This one is a toss up. With Coulson the director of SHIELD I don't see how these two will fit into the future of the MCU. There is still potential for them because we don't know how the universe will change with "Age of Ultron" and "Civil War". Maria Hill may end up appearing more on "Agents of SHIELD."
4.) Hawkeye
This just seems to much like the obvious death to me. Many people rack on Hawkeye for being the "useless" member of the team in the movies with just his bow and arrows. Fans of the comics will know that he is one of the most significant members of the team. Not for his powers but for his heart and commitment to the team.
“He has no super powers; Hawkeye’s a regular guy, one whose struggles mirror our own. We've seen our issues with confidence, our mortality, our injuries, our heartache, and our loss all reflected in Hawkeye's stories. He's the human Avenger who overcomes his problems just enough to fight on superhuman battlefields. We can't be a god like Thor, and not all of us can be a genius like Tony Stark, and very few of us can remain as unwavering as Captain America. We can be Hawkeye, though, and he's a great Avenger to be.” – Brett White
It would be a mistake to kill off Hawkeye before his full potential as a character are realized. One I highly doubt Marvel and Joss Whedon will make.
3.) Black Widow
We will be getting more back story to Black Widow in this movie. If there has to be a fallen Avenger to avenge then I think Black Widow is a safe bet. Given the scene with the hammer the movie may touch on Black Widow's "worthiness" given her dark past. A sacrifice may finally prove her "worth".
2.) The Hulk
Nothing would set Ultron apart as a villain more the being the one to kill the Incredible Hulk. It's not beyond Joss Whedon to kill off our favorite characters. With all the fake-out deaths the MCU have had (Nick Fury, Loki [twice], Coulson, Bucky) it's time Marvel kill of a major recurring character(I doubt Thor's mom and Agent Sitwell count as major). Hulk death would be emotional and unexpected, perfect for the movie in a final intense battle with Ultron. I think they also may not want a Drax vs Thanos showdown overshadowed by The Hulk vs Thanos in "Avengers: Infinity War."
1.) Quicksilver
Quicksilver is who I predict to die for many reasons. Marvel may not want to constantly have to compete with Fox. More than that I think it would be a perfect way to set up Scarlet Witch as a character. Get us feeling for this character and liking him only to than pull out the rug from underneath us would be perfect for the movie. The twins have always had a co-dependent relationship. To leave Scarlet Witch without her brother would set up most of her story arc. Also building a relationship between The Vision and other Avengers. Scarlet Witch has always been a more important Avenger than her brother. I have always seen Quicksilver as more of an X-Men Character and Scarlet Witch as an Avengers Character. And her reaction alone would be heartbreaking to watch.