SmartThings is in the middle of a transition to a completely new architecture, part of which is called Edge.
The Samsung-hosted free groovy cloud will go away. For hub-connected devices, including zwave, the DTH replacement will be Edge Drivers, which are written in the Lua programming language and will run locally on your own hub.
Here are the official announcements:
Announcement | Changes to our Legacy SmartThings Platform
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Announcement | SmartThings Edge for Devices and Automations
Edge is still in Early beta and they missed their target transition date from the first announcement so no official timeline details at the moment.