I was in contact with Matt from Grimmspeed, asking about them about compatibility for the 5th gen, as InfamousPerformance.com listed the one for the 4th gens as compatible through 2013. He said they were incorrectly listed, and that they are actually getting ready to release the EBCS for the 2015 WRX, which, you guessed it, will fit our cars. So FYI to anybody looking for a plug n play version, they're coming soon!
See the thread on Nasioc for updates and announcements of the group buy!
2015 WRX 3-Port Boost Control Solenoid