Recent reports suggest there are nearly 500 asylum seekers at the facility, which would mean about three more boatloads from Australia could eclipse the long-standing 600 capacity.
However, an information session by the Australian High Commission in Lae last week revealed that expansion work on a soccer field was being completed last week at the Manus Island centre to lift the accommodation capacity by 400.
Other expansion work is expected after the Australian federal election this weekend.
Polls suggest the Liberal-National coalition will win government. On the basis its policy promises are kept, the Manus Island detention centre is expected to eventually expand up to a capacity of 5000.
The possible re-election of the Labor party government is expected to help expand the Manus Island capacity to 3000.
At this stage the significant threats to this work are either a successful constitution-based legal challenge in PNG or Australia, or a significant decline in demand for those involved in the people smuggling trade from Indonesia to Australia.
Manus Island landowners also blocked access to key facilities last week.
However, efforts are being made to include a minimum 50% local workforce for contracts at the centre that are expected to include building new staff accommodation, healthcare and office blocks along with recreational facilities.