Until now, there is no concept of Dev or Production instance in Salesforce Marketing Cloud. With April 2019 release, Salesforce is introducing Deployment Manager in Marketing Cloud.
You no longer need to manually recreate a journey in a new account or business unit. Instead, you can use the Deployment Manager to copy the design of the journey and deploy it in other business units or enterprises in Marketing Cloud. You can also copy Journeys between Accounts (not just Business Units) with Deployment Manager.
How to enable?
You need to install the Deployment Manager app from AppExchange into Salesforce Marketing Cloud.
How it works?
Use the Deployment Manager to create a copy or snapshot of a journey. Then navigate to another business unit or account, and use the Deployment Manager to upload and deploy the snapshot. Deployment Manager then recreates the design of the original journey as a new unconfigured draft journey in the target account.
FREE. Yes, you can install the Deployment Manager app for free.
[Forward looking statement] This app is expected to be available for all customers from May 1, 2019