Well, I don't know. That's the thing, nobody knows how the transition will play out — it could end up being that there's such a significant power gap between the first "pro" AS-based Macs and current Intel Macs that not upgrading incurs a significant cost. This seems particularly likely for developers depending on the Apple dev toolchain (Xcode, LLVM, etc) where Apple can and probably will optimize the whole chain to take advantage of Apple Silicon exclusive features, making them work in ways that wouldn't have been practical on Intel CPUs.
Additionally, I can see it being a real boon for a mobile developer to have their dev machine be the same architecture as the platforms they're targeting. In the future, Xcode will likely be able to run and debug iOS apps under development without even needing the simulator (they just launch the same way Mac apps do). Android development could benefit too, if macOS' virtualization support is leveraged.