It's looking more and more like mainstream embedded SoCs will combine the general-use HMI processor core (like an A8/A9) with a smaller real-time core for control tasks.
TI Sitara (Beaglebone family) does this via the PRU, and Freescale added a Cortex-M4 to the i.MX 6SoloX for a similar purpose.
This is the definition of a hard real-time system. In most of the literature, 'embedded system' is a broader term that just means there is some compute embedded in a device that performs a larger task.