Timeline not to be a part of Fall Creators update, pushed back to Redstone 4
Microsoft’s Joe Belifore has now said that this feature wouldn’t be a part of fall creators update. It would be released to Insider builds of Redstone 4.
Correct. Timeline won’t be in the Fall Creators Update. We’re planning for it to be in early insider builds shortly after FCU is out.
— Joe Belfiore (@joebelfiore) July 3, 2017
Those who don’t know about it, Timeline was showed as an extension of the task view feature. Timeline, together with showing your currently open apps from PC would also show apps from your other devices like Android and iOS as well.