So, after the happy ending, Jackie Chan continues to be immortal forever as a frail old man. Or maybe he gets worse!
Or perhaps he like Golden Sparrow wanted to see Jason (his student) again so he had to enter this world on its own terms. Who knows when he dies in this world he will return in the other in the same state as he was when Jason left the other world.
It's a fitting disguise to be old because it's pretty rude to go asking old people how old they are.
Two questions about the ending
First, the ending fully implied that the Drunken Immortal is indeed immortal. If that's the case, wouldn't it also imply that all the events happened and all the magical stuffs ( the Jade Empire and it's magic, the Monkey King, the Immortals, the Jade Emperor, etc.) were real? Or to put it properly, All Myths Are True?
Since the ending implied that the old man is Drunken Immortal, that means he deliberately invoked a time paradox in order to have Jason fulfill the prophecy. Wouldn't that make the whole story a Stable Time Loop?
Why is Monkey King Cu Chulainn? So he doesn't have the chariot, and he doesn't go really berserk (although he incidentally beats up everybody iirc), but into this more or less Asian cast you drop a guy who looks white(ish) because of the makeup, obviously loves the whole fighting thing, etc. Admittedly I didn't watch the movie for the plot and had to go look up the synopsis to find the character name... but I'm still a little muddled on the whole thing.
The Monkey King is a Trickster Archetype. So, to some extent, is Cu Chulainn. They tend towards similarities the world over.
Why is it that the Fandom for the movie is always going on about how Jason is portrayed as a God-Mode Sue and Mighty Whitey? The only people he's shown beating are the Mooks and it took weeks (perhaps even a few months, considering he grew a ponytail) of training for even that to happen. He was clearly dominated in his fight against Ni Chang only able to get a few blows in, he knew he stood little chance against her from the beginning and was going to die if it hadn't been for a Big Damn Heroes moment and he only killed the Jade Warlord cause he snuck up on him and stabbed him with the poison dart when he turned and that was after he was weakened after facing Li and Chan.
The "Destined" part he was supposed to play was to be at the right spot at the right time to use Sun Wukong's Mighty Magical Staff to whack the statue and free Sun Wukong from his petrified state. And he did it quite well.
It's just people being racist.
If Jason is so obsessed with Chop Sockey and Wuxia films, why doesn't he immediately get what Lu means by his "empty you cup" speech? That sort of movie is always packed with such cryptic proverbs.
Let's be frank here, Jason only focused on fighting scenes, rather than the philosophy behind them. As one can see in the movie, he only knows the technique names and the actors, not the proverbs. It took JACKIE CHAN AND JET LI to drill those into his skull.
Somehow Sparrow knows the Jade Warlord was the one who killed her mother. Even though she was hidden in the well and couldn't have seen anything. Also, all that crying noises coming from the well a woman just ran away from. That didn't attract any attention? On that note, why didn't mom join baby in well?
For the second part, no space for mum. For the first, maybe the burning buildings and screams drowned her out. As to the original post, maybe he didn't kill her and Sparrow just assumed. Someone had to have found her in the well to get her out. That someone would either know or figure out what happened since the Jade Warlord was running the campaign across China. Sparrow would have found out as she grew from her adoptive family or the other orphans.
You need to see some of those movies Jason had been watching. "Hidden child can see out of a crack and has a clear view of the person that killed their parents" is a time-honored kung fu movie trope.