Except it probably won't ever happen. Charging anything turns off the vast majority of users.
Regardless, the free trial -> paid version is a popular model, even if 1 year is a long "trial"
I paid a few dollars for WhatsApp once or twice to keep it working after the first year. It was such a small amount I didn't care. I remember some of my friends freaking out about it though, like they were being tricked.
I agree for the most part though. Some uses just flat out refuse to pay money for apps, even $1.