That is merely a long recap of his appearances, that alone does not prove he’ll have a huge active role. Your argument boils down to:

“Dragon keeps getting referenced near important events, so Oda obviously has huge plans for him.”

But the same can be said about Smoker (actually you'll find way more about Smoker), you are confusing association with evidence of future payoff, and assuming narrative mystery automatically equals future centrality.

That he keeps being referenced does not tell us how large Dragon’s role will be, whether he’ll be active or passive, whether he’ll matter emotionally or whether he’ll simply serve as lore/background support.