Correction: The existing free cloud apps will remain available until March 2019. My apologies, I stated the wrong date. After that the apps will be replaced with the chargeable app solutions.
The existing free apps will continue to work and customers will not be charged to use the free solutions. However, support for the retired free apps will be discontinued after March. Customers may continue to use them, but if the service providers make changes/updates (ie; cause the apps to break), the apps may stop working without warning. At this point, customers may choose to upgrade to the chargeable apps supporting their cloud service.
I hope that this information is helpful, but please let me know if you have any additional questions or feedback.
What happens to all current customers who have that app after April? Will they get an error message that it won't work anymore and need to contact someone?
The team has been considering the move to chargeable apps for quite some time. They have spent a lot of time benchmarking our solutions against other providers. The competitive analysis has always supported charging for the apps. The launch of App Gallery v5.0 and the introduction of an eCommerce solution has made it possible for the Apps team to begin charging for apps.
The existing cloud apps will remain available to Channel Partners until April 2019. After that the apps will be retired.
As you mentioned, there are some changes introduced with the 2.0 version of the apps. Some of those differences are; updated logos, ADFS support for the Office 365 and OneDrive apps and the option to integrate with a Single Sign-On solution.
I hope that this information is helpful, but please let me know if you have any additional questions.