South Australians are still waiting to hear promised announcements from the state's premier and opposition leader - eight days before voters head to the polls.

In February, Premier Jay Weatherill said there were "rumours about the place" that SA-BEST candidates would defect from the party following the election.

"We already know members of Nick Xenophon's team are saying they will be resigning from his party within months of being elected and becoming independents," Mr Weatherill said.

He said he would release more information on the potential defections further down the track, but on Thursday remained tight-lipped.

When asked when he would release the names of the candidates, the premier replied only with "soon" and would not clarify whether the release would come before or after the election.

During a press conference on Thursday, Opposition Leader Steven Marshall withheld details of his party's public transport plan.

Mr Marshall and opposition spokesman David Pisoni announced a right-hand turn would be added to Adelaide's controversial east end tramline extension, at a cost of $37 million, if the Liberals win government.

He said the turn - at the intersection of King William St and North Terrace - should have been included in works currently under way, to take the line past the Art Gallery and to the site of the old Royal Adelaide Hospital.

But Mr Pisoni could not say whether the intersection would become a grand junction under the Liberals' policy.

"That will be clarified when we release the plan," he said.

"Today what we're saying is that we're putting a right-hand turn in, and you'll see more of what we're doing with public transport and trams when we release the full policy."