We will need to wait and see.

It might end up cheaper to ship in ammonia synthesized from solar in the tropics. Most likely it will be a combination of several: normally, delivery by transmission line because cheapest, but with geothermal held ready for strategic backup, and stockpiled ammonia for load peaks.

Shipping will get cheaper as fuel does, but is already astonishingly cheap.

In what way is shipping fuel expected to get cheaper?

I’m not aware of any significant and serious efforts to replace ships with a green fuel, and they comprise a huge percentage of our emissions.

To remain competitive, shipping will need to re-tank to burn tropically synthesized (most likely) anhydrous ammonia, which will soon be cheaper even than bunker oil. Ships still burning oil will find increasingly fewer ports open to them.

The west-African coastal Sahara, coastal Peru/Bolivia, Baja California, Arabia/Sudan/Eritrea, Yemen/Oman/Pakistan, Socotra, and north-western Australia all look like good places to site solar-driven ammonia synthesis. I don't doubt that less geographically-favored sites will dominate instead.