For smartphones, I think there's a huge amount of work still needed to make them accessible/understandable/safe for the uninitiated, including but not limited to the elderly and isolated. If, as seems horribly likely, we're moving toward a future where smartphones are not optional, something has to give.

The obvious problem is that it's not a glamorous or technically impressive thing to be working on, and isn't going to be remotely interesting to the people who'd be working on it because, well, they already know how to use their smartphones.