It's OK. It's not smooth and natural, it's not strange. It's good English, but I don't think it's very good _writing_. It could be effective in a speech, where the speaker wants to prepare the audience for the restatement. "That" refers to the original quotation. We've just heard it. He is mentally putting it over there. "This" means "what I am about to say," which is mentally closer, right here. It seems odd to me that Asian characters, who are presumably speaking in an Asian language, would use a saying that relies on a pun that only works in English! It is a play on two different meanings of the English word "present:" "now," and "a gift."

"That would mean" without the "this" at the end sounds better and would be the way I would say it, but I think both are correct English. :-) And Po "has" chosen to be a dragon warrior. I love that saying.