Leads to the discover of Battleworld. Here is my version of it happening lol.
With Grandmaster missing in 6.3 it is safe to say he will emerge as the final threat for 6.4. or not but again this is my storytelling

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Enraged and Fed up with trying to control carina and failing due to his brother interference and losing control of the battlerealm, Grandmaster has decided to take matters into his own hands.
His first objective put the summoner back in their place and remind who is truly the ultimate ruler of the realm. Of course we never backdown from a fight so we fight to save and we win.
Beaten up Grandmaster falls down on his knees and comes to terms that the summoner is indeed a worthy challenger as we have taken down the most dangerous foes ever ranging from kang to grandmaster himself.
With defeat at hand Grandmaster comes to realization that he been blindsided all this time by rage and power as he sought to be the true ruler of the contest. Collector joins him and assures him if it wasn't for the summoner they would never have brought his daugther back and thus the never ending war between them would rage on forever putting the battlerealm in harms way.
Carina begins to laugh in a sinister way saying how pathetic and weak her uncle and brother is as they couldn't harness the true power of the battlerealm and explains while she was trapped in her crystal prison she met an entity who knew what it felt like being in prison as it was inprisoned for years.
There the entity promised to teach her how to harness the full potential of the iso8 and now that she knows how too she calls out the summoner and demands a battle so she can show what true power really is.
Battle is over once again and we emerge victorious. With carina on the floor her uncle and brother run to her aid began to apolgize to her saying how sorry they are and how they let their hatred for each other led to her prisonment and almost her death.
With the 3 finally on the same side FF4 machine activates piercing when suddenly an entity emerges from it. Standing in front of them they demand to know who are they. Carina opens her eyes and tells them that is the one who taught her and its name is Entropy.
Entropy thanks for the brothers for getting carina stuck in the crystal prison if it wasnt for them he wouldnt of had the opportunity to plan his escape and also thanks the FF4 as well.
He explains he was planning to use to carina to open his prison and release him but along the way FF4 came along and decided to build a machine to escape the battlerealm and that was his ticket out but in order to escape without anyone knowing he needed a distraction thus carina was the perfect distraction.
Now free from his prison Entropy vows that he will make the brothers pay for getting him locked up and tells the summoner he cant wait to finally battle us for while in prison he witness our victories over the years and disappears.
Carina and with her dad and uncle get on their feet, another figure emerges throught the battlerealm. All 3 looking confused the figure asks where are they to which carina responses your in the battlerealm.
Figure then explains that they are from the Battleworld then the camera pans around into the portal where we see the battleworld in the distance. Screen goes blank with the words written Realm of Champions begins with the release date.
This is alot to read but i do hope you like my story even tho this is clearly not what is gonna happen lol.