Thats assumed, but if your referring to 1 John 5:7 (the Comma Johanneum), thats not enough support for a trinity, beyond the concept being recognized in a side-note or 'gloss' placed into or alongside the text. We cover that here (see all links).
All other places where John speaks of the logos do not necessarily imply or refer to a 'Trinity' per se, and even in Revelation, there is plenty of references of maintaining a Unitarian Christology, with Jesus still being the Messiah-Son, with all divine titles and appellations afforded him, without him having to be 'Almighty God' himself,...he being the anointed AGENT (agency) and representation/representative of 'God'. (here a man can be called 'elohim' as serving as God's voice, prophet, messenger, etc...since the one who comes to represent and speak for a king, is as being the King himself. -not necessary to con-fuse the two). So, one can interpret these passages EITHER WAY.
No contest really, except what you personally CHOOSE to believe and how you interpret the texts, what theology resonates best with you, etc.
1 John 5.7 is not even on our radar.