In EU the max output is 100mW of radiation.
High efficiency antennas could increase this, but the default antennas are not of that type.
Secondly the default power of a router rarely exceeds 30-50mW, some brands have options to increase this in their firmware.
Third the antennas are used to spread the signals over 3 different channels in order to accomplish the 300Mb (max) throughput.
So overall i expect no increase.