Several names are rumored to be in contention for the two key roles in the fifth "Terminator" film which Alan Taylor ("Thor: The Dark World") is tipped to be directing.
Patrick Lussier and Laeta Kalogridis are writing the script for the film which is said to be the first of a new trilogy, and is allegedly revolving around John Connor going back in time to save a young version of his mother Sarah from a Terminator.
SchmoesKnow is the one reporting the rumor today, saying that Emilia Clarke ("Game of Thrones"), Brie Larson ("21 Jump Street") and Margot Robbie ("The Wolf of Wall Street") are up for the role of Sarah, while Garrett Hedlund ("Tron Legacy") and Boyd Holbrook ("The Host") are in the running for John.
How solid is this? Frankly all five names are likely on the "potential casting list" of various projects in development (Hedlund in particular has either just missed out, or more often turned down, many high profile roles he's been linked to). Consider it highly speculative for now.