Although story of SharePoint Designer 2013 is slowly reaching its end and it is known for sure that shortly after 2020 will be deprecated, still there are many clients using it and developing their solutions with its help.
Recently ended video-conference “SharePoint Virtual Summit” (https://resources.office.com/ww-landing-sharepoint-virtual-summit-2017) confirmed rumors regarding upcoming changes and direction of the development Microsoft is planning for Office 365, in terms of “Digital Workplace” – a space dedicated for the employees, providing them with all necessary tools to make their work more efficient and comfy.
Microsoft is focusing mostly on the following products in these terms:
In my opinion this is where the most interesting changes are foreseen.