If we've learned anything about advertisers in the past, is they WILL get greedy, and start exploiting human brain in more and more ways. Eventually it reaches uncanny valley, and more and more people start noticing how messed up and over the top advertising has gotten and find ways around them or to avoid them, or in the end, neglect them.
Of course, this assumes people still 'own' their devices, at that..
Yes they will exploit it. But I think the real problem is, when you don't know if what you see/hear is advertisement.
Like seeing a news paper article which is actually advertisement. Or a blogger who says a phone/shoes/etc. is the best she/he every tried. While it's actually bought advertisement.
Of course, this assumes people still 'own' their devices, at that..