What technology is the most likely to replace the smartphone?

Given enough time; I'd say something that's similar to Google's Glass or a physical sensor stuck into one's brain (Neuralink).

What's holding back these advancements is the way companies monetise these ideas--the fact that people feel creeped out by how they can be abused. This also gives these companies enough time to iterate, though.

But my guess is as good as any.