It seems like Google might add a Multi-Window’ support in future Android updates. The possibility of the new feature has been spotted on Google’s AOSP framework commit.
AOSP framework code commit shows Google using multi-window support. Multi-windows support allows users to perform more than one task such as watching a video while taking notes or performing searches on the web. Samsung Galaxy series offers multi-window feature that lets users access two or more apps at the same time on a smartphone or a tablet.
A multi window support could be a good addition to Android but there is no other information about the feature and if or when Google is planning to introduce it. At present all we have is a glimpse of the code about the multi-window.