Imagination Technologies sold off MIPS in 2017 [1] - while RISC-V might have been a thing back then, it was certainly nowhere as known as it is today, and well before any decision to focus on RISC-V.
Interesting in that Imagination have since announced RISC-V cores [2], but that's unrelated to any of the MIPS tech, and none of the MIPS engineers worked on it as the project started well after the sale.
They don't need anything as powerful as ARM (and thus avoid the licensing fees), and it's a very price-sensitive market, so a fast 8051 + accelerator hardware is enough.
No doubt some of the more expensive ones may be ARM-based, but I think the 8051-based ones far outsell them in volume.
RV32 will turn out to be the 8051 of the present. The 8051 was the Doge Dart of embedded automation. I bought a book in Vietnamese in Vietnam in 2005 on embedded development hardware and software for the 8051. If the diagrams were any indication of the quality, the writing was excellent.
I highly doubt it. As "reduced" as RISC-V is, 8051 is still tiny in comparison.
8051s are used in applications where a 4-bit MCU (yes, they do exist and are still in widespread use) is not quite enough, or they'd have chosen one of those instead.
If all you're doing is making a core with a little ROM, a USB interface and a flash interface chances are your design is pad limited - it probably doesn't matter which CPU you use provided it's tinyish
(oh and 8051 are a pain to work with, they've taken far too much of my lifetime, they need the stake thru the heart thing)
That's still a huge difference, and as I mentioned above, the 8051 is found in applications which are very sensitive to cost. In terms of gate count, the lowest numbers I could find for a RISC-V core are in the 10-20k range, while an 8051 goes down to 2.7k:
The company that owns MIPS, Imagination Technologies, has entirely dropped the MIPS ISA to instead focus in designing RISC-V cores.