AI for helping you design and test UX, perhaps. I could see ML being used to 'simulate' eye tracking (and I'll bet some startup is working on that already).

But morphing UI based on subconcious behaviour, I'm not buying it. Short of actual mind reading, there isn't enough information in those to make a change in UI be consistent. Is my heart rate increasing a sign that I want the lasso tool in Photoshop? I don't think so.