I think there's some confusion (and misinformation) going on here.
From my understanding, current users of 7 or 8 (possibly Vista as well, not sure) will be able, up to one year from Windows 10's release date, to upgrade their (compatible/supported) machines to Windows 10 at no charge.
Users who upgrade after that point, or users creating a new desktop from scratch, will have to purchase a license for Windows 10.
There's no "subscription" pricing model that I've seen discussed by anyone reliable -- you don't upgrade, get free updates for 1 year, then suddenly have to pay for them. As with previous versions, all updates to Windows 10 for those that own it (either via free upgrade or via purchase) will be free for the lifetime of the device it's installed on.
Again, I could be wrong, but this is the most common-sense reading I can obtain from all the various information currently out there.