I think the reason I interpreted this a bit more "heavily" than you may have intended it is simply because of the lack of links to get to existing content on the site.

That, combined with the "signing off" nature of the message and that the site's nav links no longer resolve made it feel like the fact that old content could be accessed at all might have been an accident.

But it's great to know that you'll be keeping it all up there; your blog's content is an extremely valuable resource! Thank you for spending the time and energy on it over the years.