I was busy mourning the loss of Sennheiser headphones when I started poking around their web site. Under the Pro Audio page was a headphone section, with several models listed. Sadly there are no HD 500 or 600 models listed, but there are still a few pro models to be had. Such as the classic HD 280s, HD-25 and some in-ear models as well. Maybe all is not lost…if I’m reading this right.
https://en-us.sennheiser.com/professional-headphones-headsets?order_by=relevance&page=2