I do not believe Microsoft will ever do this to general consumers.
All current devices, even the ones with the free upgrade, have permanent licenses with the implication that they will not be forcibly deactivated ever. Microsoft may eventually stop pushing updates, but not until the devices and OS are horribly out of date - and the whole point of Windows 10 is to have one version that is never horrible obsolete.
All consumer devices sold now are sold with the expectation of being fully usable as soon as you bring it home. I do not believe that will ever change, as the vast majority of users are
kinda stupidadverse to tinkering with a device that exists solely as a portal to the internet and their data. Having consumers bring their shiny new "WinThing" home only to find out that they must spend a monthly or annual fee to continue using it would be an unpleasant surprise, and would have such an adverse response that any theoretical profit from the move would be swallowed by a brush with bankruptcy for everyone involved.
It does, however, make sense for companies with a full-fledged IT department. The majority of the time a company will buy a ****ton of computers with a Windows license, then wipe them all and install a different version of Windows that they paid for separately. They can save money buy buying computers with no preinstalled license, and just add them all to a pool of Windows systems then just pay to license the systems they actively use. Economy is in a downturn and you laid off a quarter of your workforce? Shut off the unneeded computers and save on Windows licensing fees. Business is booming? Fire up those old computers and reactivate their licenses. You can even let licenses flow from unused systems to used systems if your needs are changing around (I don't know, local stations that are only manned occasionally by a float? People who use laptops for one part of a project then swith to workstations for a different part?)
It will be handy for professional users. Microsoft already charges for Office 365 and Onedrive 1TB, it may make sense to offer a package that includes pro features, priority support, and the ability to swith your license between computers at the drop of a hat.
But you will always be able to buy a laptop or tablet or whatever and be able to use it forever without paying another dime to Microsoft for it to continue running. Just your cellphone carrier, internet provider, Netflix, and whatever other services you subscribe to. You will always have a choice to not pay more to use your computer.