The support of Galileo, Compass and QZSS is on top. All mayor GNSS systems will be supported. But this is not all. DR is supported by Odometer/Gyro or CAN DWP. With an accuracy of 1.8 meter at CEP95 the accuracy is amazing high also. By selecting of best GPS or Glonass satellites the performance will be optimised again. And if Europe will launch its Galileo system, then there will be always more than enough satellites on the sky. What a nice navigation future.
BTW, perfect antennas can be shipped with the Glonass module as well. Glonass modules are receiving on 1602 MHz and GPS modules are 1575 MHz. Combined GPS/Glonass modules will have a need for antennas that will receive on both bands. In the end we will win more GNSS satellites on the sky.