We have found information, that an open day will be held this year, 20th of october on friday. The day was chosen cause on the 20th of October 1944, Belgrade was liberated by the Red Army and the Communist Yugoslav Partisans. FURTHER INFO: no confirmation of foreign participants, and if foreigners are allowed to enter the base. When we have more info we will publish it.
UPDATE 2017.10.13: todays info says, that non-Serbian citizens will not allow into the base, only foreign press with pre-registration.