A comment on Android Open Source Project by an engineer states that Google would offer better dual SIM support for the Pixel 4
Google’s Pixel 3 was launched in October last year, and the smartphone has been in the news for a rumoured ‘Lite’ variant. While there is no update on the rumour, another leak has surfaced online that states the Pixel’s next generation would have dual SIM support, just like the one offered in iPhone XS and XS Max.
A comment on Android Open Source Project by an engineer states that Google would offer better dual SIM support for the Pixel 4. The Pixel 2 and 3 already offer eSIM support along with a physical SIM, but both of them do not work at the same time. This feature is called as the Dual SIM, Single Standby (DSSS). The next generation phone may get an update wherein both the SIMs would be operational at the same time on the device, which could be named Dual SIM, Dual Active (DSDA) or Dual SIM, Dual Standby (DSDS), which means the secondary SIM would be able to receive calls and texts as long as the primary SIM is not being used for the same purpose.
On the Pixel 4, Google could offer two SIM slots on one tray which would require software tweaks, or it could just provide an eSIM that can be connected to different networks through software, along with the physical tray. Google already has this setup in the Pixel 2 and 3. If the DSDS or DSDA feature is released on the Pixel 4, Google could possibly roll out the feature on the compatible older generation phones as well.