It could come in two parts, one replaceable. It makes sense if for some reason, the display part needs to be integrated more than with an HDMI cable. I think the remote control experience alone would justify it.
On the surface it does seem unlike Apple to release a two part unit, but I could see it being sort of like the Macbooks and Cinema displays. The display is plugged into the wall and then there is just one cable that has data/video and power for the external processing unit. When it's time to upgrade the processing unit you just unplug a single cable and swap it out. The display part would be expected to last through at least a couple upgrades of the processing unit.
