I've been wondering about what will happen after July 29th. This machine was granted a Windows 10 license because I used it for the Windows Insider program before the official launch. After leaving the pre-release branches, it remained activated for Windows 10 Pro. That said, I already had a license of Windows 7 Professional, which could also be upgraded to Windows 10 Pro for free. I'm not sure how lenient Microsoft will be with re-activating a Windows 10 license, especially one gifted through Windows Insider, over the phone if my hardware changes too much.
Granted, a new license of Windows 10 Pro would… only… be a couple hundred bucks. That's an annoying burden, but not an impossible barrier, assuming I even need Windows 10 as a main or virtual OS at the time. I'm still curious whether this transferable license of Windows 7 could be a cheaper route, though.
At the moment? We don't know.
Last week, Microsoft published a blog post that… strongly implied… existing Windows 7/8.x users would need to purchase a full license of Windows 10 (or just get a new PC with Windows 10 pre-installed) after July 29th. Mary Jo Foley of ZDNet contacted Microsoft for clarification, and received a slightly less firm response. “The free upgrade promotion is currently slated to end on July 29 and we encourage all of our customers to take advantage of it while it is still active.”
In other words: We still don't know what Microsoft will plan to do. The free upgrade could be extended, or they could create an official upgrade SKU that is cheaper than an official license. There might be other options too, including sending Joe Belfiore to your house to stare at you quizzically, but we'll leave the list of possibilities at free, upgrade SKU, and no promotion for now.
Note that, if you have tried Windows 10 but later rolled back after it was successfully activated, then this doesn't really apply to you. As I understand it, unless your hardware changed in that time such that it registers as a new PC, downgrading will not revoke a Windows 10 license, even one granted through the free upgrade promotion. Once you return to Windows 10, if you do, it should activate.
Finally, WinBeta says that “Get Windows 10” will be removed after July 29th, although it probably won't be an immediate change. (“… It will take time to ramp it down.”) Given how aggressively Windows 10 has been pushed, it seems odd that Microsoft will just back down after their arbitrary date. They could have just wanted to offset the inertia caused by how daunting an OS upgrade seems to average users.