System backups are generally maintained in the format and on peripherals of the current system. They really cannot be considered as archived data.
I read the Popular Mechanics article that you provided. The issues described are more of the nature of archived data. Some application programs need to keep certain files for historical reasons as well a tax purposes for perhaps six years. Generally, these files are still in the format and media of the current system.
I agree, that the future retrieval of these files must be considered. Every time there is a major system change that effects the ability to access the archived files, a conversion of these files must be performed to bring them in step with the new formats and media.
Good point, London. I'll include this issue in the document.