Personally, I think everyone that got dusted is coming back. Before the movie was released, Marvel said that all the deaths in Infinity War were permanent, and I think it just meant characters that got killed in other ways (Heimdall, Loki, Gamora, Vision), and they're going to find some way to undo everything Thanos did with the Gauntlet. Dr. Strange gave up the Time Stone to save Tony, then said that it was the only way, he clearly had some greater plan in mind.