For those who came in late, S-Voice arose in the early days of voice assistants, when Android OEMs were scrambling get something like Siri voice assistant, which launched in 2011. Samsung licensed the same underlying technology for S-Voice that Apple originally used for Siri -- Nuance Communication's voice recognition -- and set about building its Siri sibling.
S-Voice was Samsung's chosen voice assistant for its smartphones until it rebooted its voice efforts with the launch of "Bixby" in 2017. Samsung's Bixby project initially grew out of an acquisition of Viv Labs, a voice-assistant company founded by members of the original Siri team.
The Galaxy S8 and every device after it launched with Bixby and not S-Voice, so this shutdown should only affect older devices.
The affected models that have the S Voice icon on the app screen include the Galaxy A3, A5, A7, A8, A9, Galaxy Note FE, Galaxy Note 2, 3, 4, 5, Galaxy S3, 4, S5, S6, S6 Edge, in addition to the Galaxy Note Pro 12.2, Galaxy W, Galaxy Tab 4, Galaxy Tab 4 8.0/10.1, Galaxy Tab S8.4 and S10.5.