Microsoft runs a Yammer group called the Office 365 Network where a number of SharePoint experts and Microsoft employees congregate to talk about SharePoint and Office 365.
Within this group, Bill Baer announced that a Foundation version will not be shipped as part of SharePoint 2016. SharePoint Foundation has been part of SharePoint for many years as a free version shipped with Windows. As of SharePoint 2016 it looks like this version will be retired.
Bill also put up a tweet here asking for feedback on the issue. You can see lots of replies from potentially affected customers. Bill has also provided his email so you can provide feedback directly if you’re worried about losing the Foundation version in the next SharePoint.