Microsoft will keep you on like-to-like editions of Windows. For instance, if you are using Windows 7 Home Premium, you will upgrade to Windows 10 Home. Please see the list below for more details:
 
Windows 7
From Edition To Edition
Windows 7 Starter Windows 10 Home
Windows 7 Home Basic Windows 10 Home
Windows 7 Home Premium Windows 10 Home
Windows 7 Professional Windows 10 Pro
Windows 7 Ultimate Windows 10 Pro
 
Windows 8
From Edition To Edition
Windows Phone 8.1 Windows 10 Mobile
Windows 8.1 Windows 10 Home
Windows 8.1 Pro Windows 10 Pro
Windows 8.1 Pro for Students Windows 10 Pro
Windows 7 Ultimate Windows 10 Pro

    Notes:
  1. N” and “KN” editions follow the upgrade path of the parent edition (e.g., Windows 7 Professional N upgrades to Windows 10 Pro N).
  2. Some editions are excluded: Windows 7 Enterprise, Windows 8/8.1 Enterprise, and Windows RT/RT 8.1. Active Software Assurance customers in volume licensing have the benefit to upgrade to Windows 10 Enterprise offerings outside of this offer.