Specifically “The many will become one when one becomes Four.” After reading through the Triglavian Primer, specifically the part about the Koschoi and how the 3 parts of a Triglavian come together. I believe that the one or the informorph will merge with a Triglavian to become 4 instead of 3. I am not yet entirely sure on the first part but it can be fulfilled by many things including Upwell, Capsuleers joining the Triglavians, New Eden joining forces against the Drifters or the Triglavians, etc.
Title Edit - its the 6th not the 5th.