Sonny's right, Windows 10 is yours (as long as you got it the legal way ) but Microsoft have made it known that future 'updates', usually meaning additions to the os, will cost money. This is supposed to replace the cycle of new os every 3yrs..
I also go along with the concept of having to pay for upgrades after the first year.
I just don't think Microsoft has committed to any specific process yet. If the first year goes as they hope, and they are able to develop revenue streams from the OS, that may have an impact on what happens after that first year. Signing a User Agreement chang to allow for an upgrade would not be unexpected, as they have done in the past.