A prominent Google-news blog claims to have heard from its sources that the Pixel series will be upgraded to 6GB of RAM in 2019. The 2 upcoming phones are also now slated to feature 90-hertz refresh rates, a feature that is to be termed "Smooth Display". Finally, the devices will stick with the memory SKUs from last year.
https://www.notebookcheck.net/Pixel-4-4XL-now-rumored-to-come-with-6GB-of-RAM-and-90Hz-displays.428900.0.html