If I'm reading the migration info right, blogs as we know them are going away when the Wiki gets converted to the new format. I see complaints about them vanishing with their notes without a trace.
I have blogs going back to 2014, 15 pages worth, to archive and save, apparently....
The best way to save your blog posts is to Print them as PDFs -- you won't get all the banner bits and the navigation bits, but you will lose all your comments. Those may need to be copy-pasted into a file manually.
If anyone has a script that can archive blog posts, I'd love to know...