The Google Pixel 5 will have a plastic back, according to YouTuber Dave Lee. The Pixel 4a (5G) will be the larger of the two models and will be the only one to feature a 3.5 mm headphone jack. Google will announce both the Pixel 5 and Pixel 4a (5G) on September 30.
https://www.notebookcheck.net/New-Google-Pixel-5-leak-points-to-a-plastic-back-as-a-headphone-jack-is-confirmed-for-the-Pixel-4a-5G.495047.0.html
Crazy idea but... What if it has a aluminium chassis but plastic back? Thus allowing wireless charging?
I feel like Pixel 4 XL on a discount will be a better buy than new plastic Pixel 5. People who are interested in plastic phones will buy Pixel 4a. At least I'm interested in Android phone with iphone-like build quality and features, so probably will replace my pixel 3 with galaxy.