Yes, it’s been a hot topic in the MacAdmin community both on Mac Enterprise list (oh no it’s the end of the world!) and MacAdmins Slack (told you it was coming, don’t be surprised).
My professional opinion is: “Don’t panic!”
My MacDevOps conference is all about supporting MacAdmins who have been writing code as infrastructure to manage Macs. And do it while replacing macOS Server in the server room with Linux and other OS.
Xsan is staying in macOS Server so I am happy and that’s my main use for the Mac Mini and macOS Server.
I have other Mac Minis doing file sharing for small work groups and moving that out of Server.app in the last revision was unfortunate (it is in the standard OS and usable there but less manageable). There’s also Synology and QNAP NAS for small workgroup file sharing and so much more And many enterprise storage vendors for larger setups.
Imaging has been dying a slow death for years and has been replaced with a thin or “no imaging” concept supported by tools such as AutoPkg and Munki.
Profile Manager is a demo version of MDM and should not be used to actually manage Macs.
Wikis, DNS and Mail should be hosted on Linux, in VMs, AWS, GCP or anywhere other than macOS Server so no problem.
Overall it might be disconcerting to some. But change is constant. And especially at Apple change comes fast and often. We have to get used to it.
Apple to Deprecate Many macOS Server Services – TidBITS http://tidbits.com/e/17760