This seems to have happened in the past 24 hours, as as of May 31, the cached version of the iTunes page on Facebook still has content visible.
According to reports, Apple seems to have transferred the iTunes page to the Apple TV page on Facebook, which includes not only all the content, but also nearly 30 million "likes" and the original creation date of April 29, 2009.
In addition, Apple has deleted all the photos and videos from the Instagram iTunes profile, but the iTunes profile on Twitter still has content.
These blank pages may indicate that more changes are coming, and Bloomberg's Mark Gurman and 9to5Mac's Guilherme Rambo have reported that iTunes will be the next large version of independent music from macOS.TVReplaced with the podcast app. Apple is expected to release a new macOS on WWDC 2019 next Monday.
It's worth noting that although the overall functionality of the iTunes app is expected to stop, the report does not suggest that iTunes' music, movie and TV show stores will soon disappear.
Over the years, iTunes has been criticized for its bloated software, so splitting it into three separate apps will be very popular. However, Apple's phasing out of iTunes may be a gradual process.