Adobe has already started the plan to sunset Adobe DTM. You are strongly encouraged to move to launch as soon as possible.
The plan was announced in Oct of 2018 and posted here.
November 2017 Launch was released to production.
Last July (2019) they reached Milestone 1. At that time, Adobe removed the ability add new properties in DTM. This essentially locked DTM forcing all new properties to be created in Launch. You will still be able to edit DTM.
In July of 2020 DTM will become read only. This will disable creating or editing tools, rules, or data elements.
The final plan is for DTM to go dark in January of 2021.