>RAM on MCUs is getting cheaper by the minute.

It really isn't. The RP2040 has 256KB RAM. Far away from 16MB.

>now it's measured in MiB

Where? Very few so far and mostly for image processing applications, and cap out at less than 8MB. And those are already bordering on SoCs instand of MCUs.

For applications where 8MB or more is needed, designers already use SoCs with external RAM chips.

>it will only be a couple of years for mainstream MCUs having that amount on board

Doubt very much. Clip it and let's see in 2 years who's right.