后半句的there will be some visting visitng是相对于前面的visiting Australian ports而言的,如果补全了就是there will be some visting of Australian ports before the end of the year.这里不能用visit.
visit 多用于去某地参观访问,地名在钱,例如go to shanghai for a visit；
visting多用于去某地参观访问某物,地名在后,例如 go to somewhere for visiting sth.