Hi Shopify Team 
, I have a question regarding the new migration of the Shopify Developer Dashboard:
What I’d like to know is whether there’s a specific timeline for including payment extensions in this migration. I’m particularly interested in this so I can start preparing everything ahead of time.
Thanks in advance!
Yes - all partner organizations will migrate to the new platform. Partners with payment extensions have not yet been migrated. Once they migrate the process to deploy your apps is documented here.
Will we be notified once Payment extensions are migrated?
You will see in the partner dashboard that your organization has been migrated as you will see clear sign posting to dev platform / dev dashboard.