My guess is they'll lock licenses to a hardware fingerprint numbers in some way (as they already do), so a new machine or radical hardware upgrades would require a new license [1]. OEM's would likely get bulk discounts on licenses and be able to pre-install the license themselves.
Basically they'd be betting the Windows franchise on enough people upgrading their hardware every year that fees from upgraders' new licenses could support all the free riders who didn't upgrade that year.
[1] Arguably the first sale doctrine means that this might not be a restriction Microsoft can impose at the legal layer. But they'd certainly to get around any such restriction by trying to implement it at the technology layer with DRM -- refusing to provide any supported way to move their license from one machine to another.
Of course any technological restriction will always boil down to a conditional jump instruction that can be patched out, which leads to a kind of "arms race" between the pirates and the DRM. Recently there was an HN article about a (rather old) piece of software which contained multiple piracy checks to sabotage the long-term user experience of pirated versions in a way that wouldn't be immediately obvious (so users would be punished for using illegal versions, but the long-term checks would be subtle enough to slip past crackers' QA and they'd likely ship partially cracked versions that didn't patch all the checks that needed to be patched). Including deliberately deleting user data after prolonged use: http://starmen.net/mother2/gameinfo/antipiracy/