Samsung's Exynos Twitter account tweeted over the weekend:
We've been waiting for the successor to the Galaxy Note 3 for some time now, and typical expectations come along with that: a faster processor, higher resolution and improved camera. But what about the security features? Given the tweet above--complete with an eye on the screen, a tracking meter, and "Unlock the future" above it--it's possible that Samsung will be adding an eye or iris scanner to the Galaxy Note 4.
With the Galaxy S5's fingerprint recognition competing with the iPhone 5s, the next logical step would be eye security--and it's something that we haven't seen from Apple thus far.
Though this currently has "rumor" status, given that it was tweeted from the official processor's account, it's entirely possible (and likely) that we'll see an announcement before too long.
Samsung is expected to officially announce its Galaxy Note 4 in September at IFA.