I doubt that this will happen. Too much time loading and unloading and the idea that they would load another ship immediately on the other side is not a real possibility.
That sounds like a matter of ship design..... It should be possible to create a design that minimizes the ship-to-train transition.
And the ships could be made much bigger, too, because they need not be designed to fit through the locks of the Panama Canal.
There will be surge areas ~ they are called marshalling yards ~ been in use since YEAR 0 in the railroad calendrics!