Hopefully the open source blogging platforms will keep evolving and if they’re replaced, hopefully there will be migration paths so that it’s easy enough to keep the information online without a major hassle.
Keeping a backup of content in plain text or markdown format is also a handy way of keeping the content accessible but I guess we also don’t want to end up in the situation where the file format that we choose to store our information in isn’t usable/readable anymore resulting in the information becoming inaccessible; that would be sad.