I did hear about dual core CortexM7 chips being in the works from a ST applications engineer. But no concrete details about them, but supposedly its just an extra core sitting on the main bus with the same peripherals connected to it. Im not even sure if its two identical CortexM7 cores or is it going to be a smaller CortexM4 or something for doing realtime-ey stuff.
Im more interested in the STM32MP1 anyway, it has potential for being a blazing fast MCU.