Unless you plan to kill USB, 5V support is kind of baked into modern computing.

EDIT: And 8-bit can't seem to die no matter how much people try. TI's MSPM0 (Cortex M0+) chips at 39-cents this year (1k quantities) might give 8-bitters a run for their money finally though. But time-and-time again, 8-bit survives each challenge. I dunno why, it just keeps happening.

Everyone* except Arduino already did long ago.

*Explanation for HN pedants: this instance of "everyone" does not literally mean everyone; it means the vast majority of people.

Meanwhile in 8051 land... SiLabs keeps churning stuff out.

IIRC, 8 bit continues to grow. It's just that 32-bits is growing faster.