I doubt we'd see preconfigured UHD PCs. Blu-Ray support in PCs has been around for years and few computers ship with a Blu-Ray drive. Heck, few ship with a DVD drive these days.
The computers may support UHD playback, but you'd still be responsible for picking up the drive yourself and software. About the biggest benefit would be the availability of USB UHD drives. Or buy a white box PC and specify you want the UHD drive.