Yannick has released Enable3D, allowing you to use 3D objects and physics inside your Phaser 3 games.
It takes advantage of Three.js and Ammo.js and is written in TypeScript, with plenty of great demos available on the web site. There is an introduction video on YouTube, all of the source code is on GitHub and it's really exciting to see this kind of powerful plugin come to life.
There are some lovely features and demos to sink your teeth into, including the ability to switch between 2d and 3d (orthographic and perspective) cameras at runtime, as this demo demonstrates.
I'd recommend joining in the discussion here on the Phaser Forum, too.