As Australia's greatest Olympian, Ian Thorpe looked set to confirm a stunning return to the pool, there has been mixed reactions over his decision on Tuesday.

Thorpe's manager Dave Flaskas said the five-time Olympic gold medalist will hold a media conference about his future in Sydney at 12:00pm (AEDT) on Wednesday, 18 months out from the London Olympics.

Thorpe retired in 2006 but the rumor mill has been in overdrive in recent months since the 28-year-old was spotted training in a Sydney pool.

Australian head coach Leigh Nugent recently confirmed he has been in regular contact, giving the nine-time Olympic medalist advice on how to regain fitness in the pool.

ABC Sports said that Thorpe's return would be an enormous boost for an Australian swim team lacking the star power of recent years.

He would have to register for drug testing by the end of May to be eligible to contest the London Olympic trials in March 2012.

However, Olympic great Murray Rose cast doubt over the benefits of the swimming champion's expected comeback.

"It's like asking 'does the Australian cricket team need Shane Warne?' - the answer is obviously no," four-time Olympic gold medallist Rose told ABC Sports on Tuesday.

"There is an ebb and flow in every sport.

"You can't always be totally dominant.

"But if you look backwards then you are not developing your future talent as best as you can.

"And you are creating a dependence on the past that at best will last one or two major meets and then he is up and gone."

However, two-time 1,500m Olympic champion Kieren Perkins backed Thorpe to again threaten the record books at the 2012 London Games, six years after his initial retirement.

Perkins did not believe Thorpe risked tarnishing his reputation by launching a comeback.

"He is our greatest Olympic gold medal winner and he will be until another beats him and considering our current stocks that looks like it will never happen," he said.

Meanwhile, three-time Olympian Michael Klim could not hide his excitement over Thorpe's imminent announcement.

"I think it is fantastic for the sport - and Australian sport in general," Klim said.

"I am biased but I think he finished a bit early.

"I just hope he wants to do it for the right reasons."