Justin Kroll at Variety:

According to insiders, Davis would be the face of the rebooted franchise, in the vein of Hamilton’s character Sarah Connor in the first two movies that Cameron directed. Sources say Davis has been the studio and Miller’s top choice for a while, but the casting needed sign off from Cameron, who is currently filming the “Avatar" sequels.
I really dig Mackenzie Davis quite a bit - from her work on Halt and Catch Fire to her appearances in The Martian and Blade Runner 2049, even her turn in What If?.

I have to say though - this is a great pick for what will undoubtedly be a thankless gig.