Many of these SoCs are meant for netbook or even cell phone applications, so you're lucky to get 720p out of them.
Now, if these things move more into the set top box space, you could see a PVR* using a Cortex-A8 SoC that can output 1080p. (And, such an SoC would also need SATA, which would be nice to have.) With an SoC like that, one could create an even more desktop-oriented ARM-based platform.
* Before someone starts a 238 post offtopic tangent flamewar that doesn't answer an original poster's question, I'm referring to a device that has some source of TV signal going into it, records that TV signal to a hard drive for later playback, can pause live TV (by caching it to the drive,) and then outputs to a TV.