3d holographic displays, IR keyboards, powerful local llm (so more powerful), Silent-Speech Interface (SSI), more powerful cameras (better than mirrorless cameras, 3d, multi focal length in one image etc).

Oh, there's a LOT that can be improved.

3d UIs don't work, every attempt has failed to reach mass adoption

IR keyboards lack haptic feedback

Aside from enhancedprivacy, a desire to drain your battery, a lack of recurring revenue for local phone LLMs, and functioning when network is inaccessible, what would a local LLM do that a network-enabled feature couldn't?

first two features are gimmicks