Either batteries need to get better, or phones need to use less energy.
I saw an interesting phone design recently where it had two screens, one on each side of the phone. The screen for the basic stuff like making phone calls, sending text messages, browsing your music collection etc used e-ink like the display on a Kindle. These displays have the advantage that they don’t use any power until the screen gets refreshed.
The other screen was a full colour one that you would use for browsing the internet, playing games etc.
I thought that was a pretty smart idea for reducing the drain on your phone battery, we’ll see if it goes into production.