Is it just me, or does that new character really scream evil version of Zelda Wii U Link? Sorry, I just can't help but think Zelda U Link when I look at him. His face is so similar Zelda U Link and exactly like what you would see on most manga versions of Adult Link.
Plus, he even has what appears to be a cloak with a similar design choice to Zelda U Link's cloak. The designs are very similar. If you think about it, he does make you think of an evil version of Zelda U Link.
What if Zelda U really is a Twilight Princess Prequel and Zelda U Link becomes one of interlopers? He could be mislead by the actual leader of the interlopers as he stands against his tainted and depressed ancestor, the Hero's Shade! This could explain what Shade meant when he said the following:
Hero's Shade from TP said:
You have at last mastered all of the hidden skills. Although I accepted life as the hero, I could not convey the lessons of that life to those who came after. At last, I have eased those regrets. You who have marched through countless foes, each mightier then the last... You who now gaze to the future with vision unclouded... Surely you can restore Hyrule to its stature of yore as the chosen land of the gods. ...Farwell!
Could he have vaguely implied that his "regrets" were that he felt that he failed a descendant who came before TP Link?
Also, now that I think about it, I can't help but compare this idea to Captain America: Civil War! One hero (Zelda U Link in Zelda and Iron Man in MCU) sells out while the other, or rather "former" hero (Shade in Zelda and Cap. in MCU)
And one of the reasons why Link wears blue in Zelda U could imply that time plays a role again somehow and that he has a choice in end, to don the green and be a Hero, or sell out, embracing the deceiving dark light of the interlopers.
That said, Zelda U could have two final bosses, depending on which side you choose, Shade's or the Interloper leader's!
It makes sense seeing as Zelda U is said to introduce new twists and conventions to franchise and that Nintendo wants to make it where Link's actions "heavily effect the game". Implying that Zelda U could be intended to focus on the teaching the valuable lesson that actions do sometimes come with consequences.
It could be made where the player, naturally sees the interlopers as the good guys so they choose that path first, then they realize that the path they took was the evil path, so naturally, regretting taking that path, they go back and choose the side of Shade, leading to a brighter ending.
With all this said, I believe that yes, Zelda U will create a another timeline split with the next game that comes after Zelda U focusing on the bright ending's timeline's parallel to TP.