Do you think dragonites moves will change again?

yes.
no clue.

I assume so. That's why I made sure to use one of the two fast TMs I had on my SW/O one yesterday, to finally get the double dragon moveset I've chased for a year.

You can't be sure that they won't change steel wing to another non-dragon charge move, meaning that if you were to wait too long, you wouldn't be assured the dragon charge move with a fast tm.

After that, who knows? Maybe Outrage will get nerfed. Maybe Hurricane will get buffed. Maybe it will be legacied for something better (or worse)?

Yes.
They changed it when gen 2 came out, maybe they will do it again once they release gen 3. When is that, I have no idea.

Let me bust out my crystal ball