Is the sun about to set on Sunrise's veteran co-host David Koch's time on the all-important breakfast television throne?

It's a question being asked around the corridors of Channel Seven, with the 62-year-old and his agent, Sean Anderson, deep in negotiations with Seven bosses for a new contract, said to be worth up to $1 million.

Koch is understood to have requested he go on a four-day working week with Sunrise, freeing him up to work on his other projects, including his beloved Port Adelaide AFL club and his private finance marketing company Pinstripe Media.

But it is those extra-curricular activities which are said to have frustrated Koch's colleagues, some feeling he is over committed.

Koch's manager Anderson declined to comment when contacted by PS.

However PS understands relations are not quite as cosy within the Sunrise "family" as the glossy breakfast show's marketing campaign would have us believe.

While Samantha Armytage is understood to be paid considerably less than Koch, she is seen within the network to have a much longer career ahead of her at Seven. In contrast Koch is embarking on a retreat.

There is also speculation about relations between Koch and Armytage, with insiders confirming this week there had been mounting behind-the-scenes tension between the pair.

In recent weeks a veritable cavalcade of Channel Seven's leading men have been co-hosting Sunrise with Armytage, in what insiders have described as an "auditioning" for someone to fill in for Koch.

However there is also some suggestion that the fill-in role could become more permanent, with Seven keen to "refresh" Sunrise's talent line-up. Koch has been co-host for the past 15 years after filling in for his predecessor, Chris Reason, who  vacated the role when he was diagnosed with cancer in 2002.

One of the front-runners for a role on the Sunrise couch is Perth-based Basil Zempilas, a relative unknown on the east coast but well known to West Australian audiences where he is a popular TV fixture, especially on the annual Telethon.

Zempilas has just completed a stint filling in for Koch while he was on holidays. He is also said to be a personal favourite of both network proprietor Kerry Stokes and chief executive officer Tim Worner.

The all important on air chemistry between Zempilas and Armytage is also said to have played in the Perth newcomer's favour.

"It's been really refreshing, the dynamic is totally different between them compared to when David is on set with Sam," a close observer informed PS.

Joining Zempilas in the running for a bigger role on Sunrise has been newsreader Michael Usher and Matt Doran.