Byrne confirmed last August that he would not be returning to co-host the RTÉ show. Doireann Garrihy takes his place when it returns for a sixth season on Sunday.
“Of course he was right, that was always his sideline. That was a nixer for Nicky,” said manager Louis Walsh.
Despite being a man down as Mark Feehily battles pneumonia, Westlife headlined the New Year’s Eve festival with an outdoor concert beside the 3Arena in Dublin, attended by an estimated 40,000 revellers.
The band will take a few weeks off touring before taking to the road again.
Walsh revealed that their Wild Dreams tour, which they brought to the 3Arena last month, is doing “amazingly well”.
“It’s the best show they’ve ever done because every single song is a hit and it’s like the soundtrack to so many people’s lives in Ireland,” he said.
“People can’t get enough of them so they’re going to keep touring, they are going to Asia and China – they’re going everywhere this year.”
The band, which formed in 1999, also made their debut at Wembley Stadium, with two packed shows at the venue last August, becoming the only Irish band apart from U2 to play there.
Westlife will play venues in Asia including Thailand, Jakarta and Singapore next month as they perform for legions of fans.
As well as managing his long-running act, Walsh is also mentoring his new boyband Next in Line, a five-piece who were picked after a series of live auditions in Dublin last year.
Conor O’Farrell, Nueng Kelly, Harry O’Connell, Conor Davis and Joshua Regala have already recorded several songs in a studio in London with acclaimed songwriters, including Kodaline’s Steve Garrigan.
Walsh said he is determined to take his time getting the perfect songs for them.
“I’m going to wait until they have the right songs recorded before we got to a record label but I’m not going to rush,” he said.