This is the leaked picture of the supposed upcoming Nikon mirrorless mount and sensor:-
via Mirrorless Rumors
And then let's look at the comparisons made by a DPR poster as below:-
Above: Upcoming Nikon Mirrorless (Left) Vs Pentax Q (Right)
Below: Nikon Mirrorless (Left) Vs Micro-4/3 (Right)
via 1001 Noisy Camera
The quick conclusion is that the Nikon sensor will be right smaller than the micro-4/3 in size but yet still much larger than that of the Q.
Related:-
How Large a Sensor that Pentax Could Put Into the Q?
Another "Q" is Coming - The NIKON Q?! Kidding?
Leaked Pentax Marketing Q&As in the P-Q Pre-Release Press Conference