Even if someone did attempt to summon Bahamut again it wouldn't likely even look like the Bahamut we saw in 1.0/2.0 really. It seems like for a Primal to remain a particular shape seems like it needs people to believe in a particular form or appearance. It's the reason why when we summon Primals during Eden they have almost nothing in common outside of general attributes because it was forged from our Character's memories then any kind of unified belief.

Though most people saw the impact and experienced the calamity, not all of them probably witnessed Bahamut directly which would impact the ability to summon it in the form we know him as. It would probably be a completely different primal at that point.