Although only Apple knows for sure, I would be almost certain that M1 and M2 MacBook Airs will not be able to support more than one external monitor. (The circuitry inside the Mac is more of a limiting factor than software).
I don't know where you read the M3 MacBook Pro will get a software update like you described. That's the first I've heard this rumor. And just to be clear, it's only the M3 MacBook Pro that has this limitation. The M3 MacBook Pro with the M3 Pro and M3 Max processors can support multiple monitors.