Windows 10 is a free upgrade only for the first year. I also don't understand what happens with my Windows 8.1 license after that ... so if I format my laptop

Windows 10 is a free upgrade only for the first year. I also don't understand what happens with my Windows 8.1 license after that ... so if I format my laptop after that first year, will I still be able to install Windows 10 on it? I'm not so sure I can, plus their wording on Windows receiving upgrades for "the lifetime of the device" is confusing; so does this mean that the notion of a retail license that you can move between PCs is gone? So you see, Microsoft has yet to reveal their new licensing model, therefore I wouldn't be so quick to jump to conclusions ;-)