You'll have to prize C and C++ from the cold dead hands of the embedded programmers. Most of them are still doing OO using plain C.
I also think that Zig has a good chance to become popular in the MCU space.
OTOH a bigger ARM core can very well be found on a small embedded computer, and it's capable enough to run something like a browser. At this scale, pure C becomes burdensome, and libraries (like a browser engine, or Qt) are in C++ anyway.
In the case of Arduinos? Yes. As I said, the original Arduino IDE has partial C++ support. Classes are used by almost every library. The AVR series originally targeted are 8 bit MCUs, and they run fine despite the ATMega328p, for example, having only 32 KB of flash.