Samsung's ubiquitous Multi-Window feature might be coming to stock Android in future updates. Google's recent AOSP comment mentions multi-window support in passing.
If you have used recent mid-range Android smartphones, Multi-Window allows you to perform more than one task at a time by dividing the display into two or more sections and pinning apps to these. Multi-Window will also allow for floating apps, wherein you would be able to reduce the size of an app window and let it float over other apps.
With the recent trend of large phablets multi-window support in stock Android can be a great boon for multitasking and power users.
