As mentioned on the HGGS website:
The Holy Grail Guitar Show will take place on May 5 – 6, 2018 in Berlin. As you can see the Show is moving to a Spring date, but it will remain at its current location, the Estrel Berlin. So there will be no Show in 2017.
To get an idea of the magnitude and scope of this great exhibition, check out the 2016 catalogue in PDF.
Looking forward to this amazing show!