What do you notice from this eligibility list? Windows Enterprise editions and Windows RT are specifically excluded.
Windows RT is likely being replaced with Windows 10 mobile edition anyway so more will become known on that in the next few months. Windows 7, 8 and 8.1 Enterprise edition are not eligible for the free upgrade offer so how would those customers acquire Windows 10?
Customers with Software Assurance (SA) on their Windows licences have rights to Windows 10 Enterprise through the software assurance new version rights benefit.
In the days when you acquired Windows Enterprise by buying Windows Pro + SA, your underlying licence was Pro but even if you stopped SA you could retain perpetual rights to enterprise. In this case you could revert to Pro edition and go for the free upgrade. That does involve a reinstall though so not a nice option.
Or you could buy Windows 10 Enterprise + SA all over again. Possibly not an option which will be greeted by cheers.
Or you could go for Windows 10 Enterprise without SA and stick with the Long Term Service Branch.
Limitations with the Upgrade
The Windows 10 licence created during the upgrade is a consumer licence that is tied to the device. The licence will continue to work for reinstalling Windows 10 after the free upgrade period ends but only on that specific device. so if you need to replace the hard drive or do a reinstall for any reason other than replacing the motherboard, it will work.
For volume licensing customers, the licence created is not a Volume Licence (VL) and will not be in VLSC (Volume Licensing Service Centre). Whilst there won’t be any differences in the end-user experience between the free upgrade and a new VL purchase of Windows 10, the licence is different. If you buy Windows 10 Pro through VL, you could not use the image or keys from the VLSC to apply the upgrade for free to other, unlicenced machines. At present the Windows 10 Pro Upgrade licenses will be priced the same as the existing Windows 8.1 Pro Upgrade licences in case you do want to buy the full edition.
A couple of last points; even though customers on Windows 8 will get a lot of nudges to upgrade to Windows 10, Microsoft will not force people to upgrade. They can remain on Windows 7, 8 or 8.1 and the support lifecycle for those remains in place.
Education customers have the same criteria. Upgrade goes by the eligibility of the device and installed operating system; nothing special or limited for education.
See part 2 of this blog post for information on how Windows 10 is becoming an evergreen service.