But as I said before, the Natami already is planned to have the Robin core which is probably the same technique used internally as the XCore system.
Not at all. Natami uses an FPGA which is more or less an electrically reconfigurable custom chip. You write a description of the hardware you want in a language like VHDL or Verilog and the FPGA gets configured to act like a chip designed to your description.
The XCore from XMOS is basically a microcontroller (CPU plus some other stuff on the same chip). It's a little funky (8 hardware threads is an unusual feature and the main thing that differentiates it from other offerings), but it's still built like a CPU and writing an emulator to run on it wouldn't be that different from writing one for any other CPU whether it be PowerPC, x86 or something else.
Now for all practical purposes, emulating something in hardware doesn't necessarily give you any benefit (unless your CPU is too slow of course). So the distinction between hardware and software isn't all that important (but I tend to be a bit of a pedant).
Without more details about how the XCore is integrated to the rest of the system. If it can read and write directly to main RAM and access the rest of the hardware, offloading emulation tasks to it might make sense, but if the connection is more limited then you might spend more time shuffling data back and forth than you save.
