The M1 and M2 do have different microarchitectures. And at some point, Apple will need to make a cutoff to drop the first generation(s) of AS machines.
But whether they do that just for the M1, or group the M1 and M2 together (or group the M1, M2, and M3 together, etc.), we don't know. That's because there's no one here (other than those who work for Apple and thus can't say) who knows enough about how the uarch interacts with the OS to know whether M1 and M2 are close enough that, when the cutoff is done, they will be grouped together or not.
Indeed, even the Apple software engineers themselves may not know, since they've not yet written the OS's at which M1 and M2 would be cut off. Thus this may be a determination that even they can't make until then.
Hence I'd suggest you choose based on a cost/benefit analysis comparing what the two would provide you with today.