Yes, the challenge is the software. Not so much the native Mac software created with XCode. That would probably rebuild at a button press. The elephant in the room are VMs. Many Mac users (for example me) are running x86 based operation systems inside VMs on their Mac. This wouldn't work without a dynamic translation like Rosetta. But as Apple is making their own processors, I would consider it a possiblity that they add some hardware accelerators for a Rosetta style software to their chips.
While I understand running VMs are important for you and many developers, people like us who want to do this have to be a miniscule share of Apple's market. I wouldn't bet on them spending much time on it.
You are right that developers are only a small part by volume. However they are the most important users in an environment, as they the ones creating new applications. Same with other power users, who require a VM. Driving them away from the platform could have a much larger net effect. That Macs got much more popular after the switch to x86 hints at that the compatibility isn't quite unimportant.
So I do think that Apple is probably going to ARM, but they need to be very careful in the steps they are taking and they need to have a really compelling offer so that users are willing to go through the transition.
