The following theory is based on post 5chan post. And it is rock solid.
Based on the information provided in recent interviews with president Toshihiro Kondo, poster argues that there is a good chance that the Awakener of the Golden Deus-Excellion is Renne.
Posters continues that the knight is named Gordias. The term “Gordias-class” has been around since The 3rd. The Gordias Type-0 is the prototype that went on to become Pater-Mater. You fight (a copy of) the Gordias Type-0 during Trails in the Sky The 3rd‘s final boss rush. That’s right, that golden Pater-Mater. Renne, or Joshua if you don’t have Renne in your party, says that it might be even stronger than Pater-Mater. Think of Gordias, the Golden Deus-Excellion, as the base for the “Gordias-class” mechs.
How does Rufus’ suspicion fit in with this theory? As the governor-general of Crossbell, he knows the area he controls very well. Poster continues that Rufus’ thoughts may have directed toward the Doll Studio, ran by Gordias-class constructor Jorg Rösenberg, or the ruins of Lake Elm.
Furthermore, Renne was the only one that survived and passed the synchronisation/connection tests, as we’ve been able to read in much detail in The 3rd‘s Star Door 10: Gordias-Class Experiment Report. Like (most) other Awakeners, Renne also suffered from a (near) death experience: she was found in a highly critical condition in the D∴G Lodge before Joshua and Loewe came to rescue her.
Then there’s the promise between Tita and Renne. It is this promise that motivated Tita to finish, polish and improve the Orbal Gear. What exactly they promised, we don’t know yet – but having lost Pater-Mater, that promise might push Renne, who Kondo said could change the situation in Erebonia, to become the seventh and last Awakener.