luk - It is possible that content *beyond* the 50K limit would have been indexed at one time if it is a slow build.
In my case - we migrated >80K records; won't work for me.
Other non-conforming (to that solution) use-cases could be very-high-volume sites, mass-content updates?
I admit I don't know a ton about how Google decides to index/re-index but I wouldn't be surprised if it finds record 50,000 one week and not the next (when it comes back to check the sitemap and that item has fallen off at position 50,100) I wouldn't be surprised if there is some logic to deprecate/slash that content from their own index.
For long-lived, or high-volume communities I still think this isn't good - UNLESS I'm just not asking the right question and it is well and truly solved. Khoros Support indicates that split sitemaps is supported and Google's answer is "split the sitemap" - so I think we are still in limbo 😄
