Super Rugby bosses are considering splitting the current three-conference system into two from 2016 and adding two teams from Argentina.
Under a possible Super 18 concept which appears the most logical future competition, Australian and New Zealand sides would combine in their own conference while South Africa and Argentina would join to form a separate conference.
Leading administrator also revealed there is the possibility of Japanese teams being added in three years' time, but there is lots of work to be done.
Super Rugby expansion is certain to occur after the 2015 World Cup with governing body SANZAR committed to ensuring the recently-relegated Southern Kings will be one of six South African teams.
While SANZAR, which aims to finalise its next model by the end of 2013, has plenty to consider before deciding upon its preferred concept, the three-conference system appears to be coming to an end.
SANZAR CEO Greg Peters said the time-frame for the tournament - currently played over 21 weeks, including three weeks for play-offs - could not be extended.
That makes it virtually impossible to keep the current structure if new teams are added as the Australian, New Zealand and South African rugby unions want their local derby matches to be played at home and away.
With the rigours of travel to and from South Africa combining to make player welfare a bigger issue, the simplest solution is for a two-conference split.
That would see the five Australian sides playing each other twice and the five Ne Zealand teams once for 13 matches before both conferences came together in a six or eight-team play-offs series.
AustralianRugby Union chief Bill Pulver, who is also on SANZAR's executive committee, said the ARU had not decided on its preferred model but stressed the five Australian teams would remain.
"We're trying to keep a very open mind to what this structure looks like," he told AAP.
It is more likely two new Argentinian franchises, rather than one, would be added to what would become an eight-team South African/American conference.
That scenario would allow all teams to play home and away over 14 rounds.
The heavy political pressure for South Africa to have six teams only intensified when the Port Elizabeth-based Kings lost a closely-fought two-match relegation/promotion play-off with the Johannesburg-based Lions last weekend.
"We really understand the desire for that from South Africa," Peters said.
"The Kings have 32 per cent of the playing population and 72 per cent of that is coloured.
"We understand the need for six teams in South Africa."
While there are massive commercial benefits with the inclusion of Japan before it hosts the 2019 World Cup, there are logistical problems in fitting them into the Australasian conference.
SANZAR and the ARU are both pushing for the June international window to be moved to July to ensure Super Rugby can be played in one complete block instead of being interrupted for Test matches before the play-offs.