"How many people will be frustrated to see their devices not automatically syncing because the wouldn't know about all this technical nuances or they forgot that they still had an app running."

Not as many as you think. I imagine most people aren't doing something on their iPod when they plug it in. Either way, Apple likely has stats on this. I understand your point, but then, how many people sync via iTunes? I mean, the actual Sync button in iTunes. How often does syncing actually need to take place?

And, the same question could be asked of the interruption. How man people plug their iPod in while using it and suddenly find that it takes over whatever they were doing. It takes over, without even asking.

"Another option would be to continue the audio process after syncing the device."

That defeats the purpose. And it's bad design. Why interrupt what the user is doing? Mac users love to comment on having to restart Windows for updates. No.

"Canceling the sync on the device, which would still stop the audio process or disabling auto sync to not be bothered by it while listening to audiobooks, but be bothered to hit sync while updating podcasts."

I have the perfect solution, I would [SYNC]