Sadly, I just checked Adorama's website again this morning. Apparently they got a few in, but are now listed as "Closeout".But it has disappeared from stores and Canon website at times. That starts the rumors.
Sales is the key to finally retire a lens. Sales of both cameras and lenses has been dropping, so some will go away. Canon is going to shrink, they continue to reduce staff, so it is plausible that slow selling lenses and bodies will be discontinued. There are a few in that category that are good lenses but are dated and unpopular now.
I hate to see them go, they are a way for someone to get a excellent lens at a reasonable price.