In this article, we are going to upgrade win7, win8 and win8.1 computers to win10 on SCCM v1511and we will be using build in upgrade functionality of SCCM v1511. Navigate to Software Library > Operating Systems > Operating System Upgrade Packages, Click Add Operating System Upgrade Package.
Browse the Win10 Media
Click Next and complete the wizard and then Distribute the upgrade package to DPs
Create a new task sequence
Specify the task sequence information on the next window
Select the upgrade package that you created earlier
On "Include Updates" section choose the option that complies with needs
On "Install Application" section choose the option that complies with needs
At this point, all you need to do is deploying the task sequence to desired collections.
In my test, I noticed that TS fails if your client version is not 5.00.8325.1000.