So what is the point of a sequel? (other than money)
In the original Tong Po was a villain again which was a TERRIBLE idea. Once you establish that a seemingly unbeatable villain in a martial arts movie can be beaten the metaphorical "mountain" has been climbed and you cannot reuse him as a villain, its just boring because they have already been proven to not be unbeatable.
Reusing Boyka in Undisputed 3 and 4 was not a problem because since he switched over from a villain to a hero role he no longer had the burden a villain has of seeming invincible and being undefeated. There is no literary rule requiring the HERO of a story to seem invincible, they are SUPPOSED to be the underdog (think Rocky or Karate Kid).
But in this there is a "new villain" in the sequel. I think the whole point of this movie is that Tong Po was the all around best fighter in the world (for the fictional world of the film) then we find out NOPE there is someone even tougher? It kind of cheapens Tong Po. He is dead so this cannot happen but it kind of makes me wonder how Tong Po would do against that huge muscle guy in the sequel (I think it would be like Sagat from Street Fighter facing Hugo Andore).
Will there be a 3rd where he has to face an "even tougher" opponent? Pretty soon Tong Po won't even seem like that big a deal, kind of like how Clubber Lang from Rocky 3 seemed like small potatoes compared to Ivan Drago in Rocky 4.
Also, I kind of wanted a happy ending for the hero and with each movie he will get more scarred up, more PTSD and more trauma. Even if he wins all his fights (and he will since hes the main hero) by the end of it all he will be a physically and emotionally broken man covered with ugly scars (assuming the makeup artists work to avoid the continuity error of failing to put scars on him) and he would realistically suffer brain damage and other injuries (winning does not mean you won't get hurt) so by middle age the guy will be an unhealthy wreck.
I do not realistically see a happy ending for the character.