They are worried that if data is stored in a medium that is not Free/Libre that whatever is used to read the data will be discontinued/made prohibitively expensive and the information will be effectively lost.

I'm of mixed feelings about the situation, but tend to agree.

The biggest sign of hope that I see is that many programs use either open or simple enough standards that non-authorized/non-supported software can open it. However, this is always subject to change.