Hit West End shows may not return to the Wales Millennium Centre "without a Covid-19 vaccine", it has been warned.
Visiting tours of The Lion King and Phantom of the Opera to Cardiff have been cancelled as the £125m venue, which shut in March, remains closed.
Artistic director Graeme Farrow said it hoped to stage "test events" with about 150 people in the audience in January.
However he said the venue cannot "flick a switch" and fill a 1,800 capacity hall.
Mr Farrow has said discussions with Welsh Government had started in a bid to allow test events to take place, involving about 150 people sat at cabaret tables spread across the venue's main stage.
Productions were cancelled when the UK shut down because of the Covid-19 crisis in March and the WMC remains shut to the general public "until April 2021 at the earliest".
It estimated the venue would lose £20m in commercial income this year and said in June that 250 jobs were at risk.
The WMC received £3.9m from the Arts Council of Wales's cultural recovery fund earlier in the week to help them through the pandemic.
But the venue has now made 63 permanent members of staff redundant due to the financial impact of the coronavirus crisis.
But Mr Farrow hopes performances can return in the new year.
"We want to run a series of test events for live performance with audiences," he said.
"We think we can start testing that from January with the audience on the stage and not in the stalls.
"Because come the summer or the autumn, without a vaccine we won't be able to just flick a switch and have 1,800 people back in this auditorium.
"We need to be able to plan through for that from early in the new year with small audiences, then we need to test 250, 500, 1,000 before we can even think about reopening for big shows.
"At the minute we are thinking May at the very earliest for that, and that may move back. But we will plan for every scenario, and what the money gives us is the ability to do that with people."
Six and Everybody's Talking About Jamie are set to become the first musicals back in London's West End in mid-November, eight months after the curtain came down.
Other theatres are also experimenting while Covid restrictions prevent them resuming traditional shows.
Theatr Clwyd in Mold has held outdoor performances and has begun experimenting with streamed online events, while Sherman Theatre in Cardiff has made a series of audio plays by new and established writers.
But while Welsh Government guidelines currently prevent theatre shows from going ahead, Theatr Clwyd's artistic director Tamara Harvey said she hoped the rules would change after the firebreak lockdown.
"The frustrating thing for us is that we had a whole autumn season ready to go," she said.
"The theatre is laid out as a cabaret space with socially distanced seating. We are able to bring people into our cinema, so we know we can do that safely, and where pubs and restaurants are still allowed to stay open that has been really frustrating.
"We are really good, in theatres, at keeping people safe and keeping them in their seats."
Wales Millennium Centre has called for similar rules for live events as those which exist in hospitality.
"How can cinemas open but this place can't? Even if we were to put 50 people in this auditorium, we could have them 10 metres apart. But we can't," added Mr Farrow.
"I think we need to start asking the question 'Why not?' rather than 'Why?'."
The Welsh Government said its programme of pilot events with spectators at both outdoor and indoor events has "been put on hold, the public health position takes precedence".
"We understand this is a very difficult time for the sector and we will continue to work in partnership towards a safe reopening when the time is right," said a spokesperson.