The hreflang tags in all languages are pointing to blog-abc version based on the lang. To update hreflang tags in other languages we will have to republish them as well. Because we are trying to make the pages as static as possible, it may not be an option to update hreflang tags dynamically. The options we have is either update the hreflang tags periodically (say once a month) or move the hreflang tags to sitemap. Here’s what the research paper (PDF) says in passing about adding new pages to a search index:“Consider the realistic scenario wherein new documents are continually added to the indexed corpus.