Will the Living Tribunal be in the MCU?
Per Marvel Canon, the Living Tribunal does exist in the MIC. In fact, there is only one Living Tribunal, and he spans all Marvel media outlets: comics and other books, movies, live action TV (e.g., Agents of SHIELD and The Defenders), and animation.
Aside from the Watchers, the Living Tribunal is the other character to exist without duplication across all Marvel media. And there is some debate about the Watchers.
As to whether we'll see him in the movies, we can only hope.
The Living Tribunal has a vast amount of power and was pretty much all powerful before All new, All different marvel. It's likely that the MCU won't directly show or portray his power but he will definitely show up in some form or another.
He has already been confirmed to exist within the MCU since "The Staff of the Living Tribunal" was mentioned and used in Doctor Strange.
Odds are kind of low I think, there is no indication they are going to go full abstract cosmic with the next 2 Avengers movies and that is where we'd see him. He could show up in a Doctor Strange sequel but I just don't think they are going to introduce it.
He already is.