RNZ reports the Forum was established in 1971, creating a separate organisation that shut out the old colonial powers which dominated the SPC, which later became the Pacific Community.
But earlier this month at the Forum's summit in Pohnpei two new members were added, French Polynesia and New Caledonia.
Their inclusion effectively means France is now part of the Forum.
Dr Malakai Koloamatangi said there could well now be interest in joining from many of the other major powers that have growing interests in the Pacific.
"In fact it could become ironic in the sense that it could become the old South Pacific Commission, that the Forum was set up to counter - the SPC as it were in another guise."
"It's all very interesting and will be interesting to see just how the bigger metropolitan countries, particularly on the edge of the Pacific, react to this - such as Japan, the US, China and so on," he said.
The president of New Caledonia, Philippe Germain, and the president of French Polynesia, Edouard Fritch, after their territories were admitted as full members of the Pacific Islands Forum. Photo: Office of the President of French Polynesia