"They won't go completely extinct, the way mainframes haven't. But they'll get relegated to smaller and smaller niches."
The small screen size of a mobile phone will always limit it's suitability for particular tasks. I can't imagine any office, for example, replacing their desktop PCs with smartphones. That's hardly a niche market. Smartphones are good for consumption, but not so good for creation. For example, even the simple task of word-processing is painful on such a small screen using an on-screen keybboard.
The small screen size of a mobile phone will always limit it's suitability for particular tasks. I can't imagine any office, for example, replacing their desktop PCs with smartphones. That's hardly a niche market. Smartphones are good for consumption, but not so good for creation. For example, even the simple task of word-processing is painful on such a small screen using an on-screen keybboard.