Just a note on 2016 Migration!
Just as is expected, Microsoft will provide a native upgrade option with SharePoint 2016. Of course, the native upgrade isn’t your only option and may not be your best option.
The Native Upgrade Option
The native upgrade option, provided by Microsoft, relies on a “database attach.” This means taking your existing content databases, “detaching” them from SharePoint 2013 and “attaching” them to SharePoint 2016. As they are attached, your content databases will be upgraded and the contents of the database made available through SharePoint 2016.
Yes, you read that last paragraph correctly – the native upgrade option is only supported from SharePoint 2013. More specifically, it’s only supported for SharePoint 2013 environments that have database versions of 15.0.4481.1005 or higher. It also requires that all site collections in each attached database are in SharePoint 2013 mode, which is also known as compatibility level 15.
In other words, if you are running an earlier version of SharePoint, have not yet applied the latest updates to SharePoint 2013, or are taking advantage of the SharePoint 2010 site collection mode, you’ll need to get to a supported version of SharePoint 2013 and update the compatibility level of your site collections before you can upgrade.