There will be no fireworks - at least not from Pope Francis. Will there be drama? Could be, but not from any collision. Rather it will be in the very opposite- the stark divergence.  I suspect Pope Francis will speak plainly, clearly, briefly of what he holds and let it stand. It will shine in counter-distinction to the "how" that Trump might pretend agreement or the "what" of which he does not agree. 
Pope Francis will speak to the world of those who might listen.  Trump will posture for himself.