To start with, Windows Phone 9, aka Windows Threshold, is said to bring split screen multitasking to bigger phones. That would let you run two apps side by side like you can on a computer.
The rumour also says that Windows Phone will soon get actionable notifications, which would let you respond to messages and other notifications right from the Action Centre. That means you wouldn’t need to stop what you’re doing to open a new app to respond to a text message or anything else.
It’s thought that Windows Phone 9/Windows Threshold could be previewed at the start of next year, so we might only have a few months to wait before we see these useful new features.
Source: Nokia Power User