There's nothing stopping a person from putting an ESP on a RPi B board format (or a Zero one), other than certain IO limitation. The upcoming P4 might be a candidate [0]. If you are interested in sbc in Pi form factors (B, Zero, CM3, CM4), then something I follow is CNX [1]. It will typically have notifications of any new Orange Pi, Libre Computer, etc.
It might make sense given pi2040’s PIO capabilities. Additionally, the RPi5’s io chip, RP1, might have some similar tricks inside.
The Raspberry Pi Pico has a fascinating peripheral known as the “Programmable Input/Output” (PIO). This device allows us to write very simple assembly programs to emulate a number of different peripherals and communication protocols.
RP1 is our I/O controller for Raspberry Pi 5, designed by the same team at Raspberry Pi that delivered the RP2040 microcontroller, and implemented, like RP2040, on TSMC’s mature 40LP process.
0. https://www.espressif.com/en/news/ESP32-P4
1. https://www.cnx-software.com/news/raspberry-pi/