It seems that the Galaxy Z Flip4 will offer significantly better battery life than its predecessor. Not only will Samsung's next-generation foldable rely on the more efficient Snapdragon 8 Gen 1 platform, but the CCC in China also appears to have confirmed a notable uplift in battery capacity from the Galaxy Z Flip3.
https://www.notebookcheck.net/Latest-Galaxy-Z-Flip4-leak-points-to-a-battery-life-boon-for-Samsung-s-next-generation-foldable.621037.0.html