So I was reading online and found what the name of the second transformation that was shown in the trailer was. It’s called Mythix and will be the next transformation for the season, here is the official summary from the winx wikia page.
"Mythix is the second transformation of the sixth season. The Winx will need it in order to enter the Legendarium. The transformation will be both in 2D Computer Graphics and 3D CGI Animation just like the Sirenix transformation."
My prediction about this transformation is that it will focus on the power of Myth, so the girls will have power to fight the “REAL BAD GUY OF SEASON 6” which seems to live in the Legendarium for right now. Hopefully the new transformation will give the girls back their powers and make them even stronger.