When we did DTM to launch migration for our customer we got following breakdown from Adobe on the DTM deadlines,
1. July 9, 2019 (already passed) – Option to create new DTM properties no longer available
2. July 14, 2020 – All DTM properties become read-only
3. January 12, 2021 – DTM servers go to sleep
DTM to Lunch migration can be done by 'Upgrade to Launch' option available at DTM side easily and this option is available for Admin users however it really depends on the kind of DTM implementation and also usage of custom scripts you have in place. As some of the existing methods are deprecated in Launch definitely a thorough testing is required before you publish the property at Launch side.
Also please note that 'Upgrade to Launch' option only points the production property so even after publishing the property for development activities you will have dependency on DTM to Launch switch tool until you ask vendors to replace your DTM scripts by Launch scripts inside the website code.
