The former All Black has made his first official appearance as a Toronto Wolfpack player in London at a packed media conference at Arsenal's Emirates Stadium, as he prepares to embark on his new sporting adventure.
Williams has signed a two-year contract worth $10 million to become the face of North America's first professional rugby league team ahead of their English Super League debut.
Although he hosed down prospects of returning to Australia, he still has eyes on a potential bout with Gallen should the former NSW and Cronulla skipper beat ex- Sydney Swans star Hall in Melbourne this weekend.
"I'll be 36 once this contract finishes so I can't see my myself moving back to Australia any time soon," Williams said.
"My wife might love living in Toronto, who knows, we may end up living there. I never expected to be sitting here right now but we are riding this wave and it's exciting."
Williams continued to box in the off-season during his stints with Sydney Roosters and New Zealand, and said he'll continue to do so with his new team.
"I've had that (boxing) clause throughout my contracts. Whether it will be Paul Gallen or Barry Hall ... time will tell," he said.
"I'm pretty interested in that fight. There has been a lot of talk from both camps. I am not sure who'll win.
"Barry has been out of the ring since he was 18 and is 42 now. Gal has been fighting consistently for the last few years and that may give him the advantage."
Williams, who won premierships with Canterbury and the Roosters, had intended to stay in Super Rugby with Auckland Blues in 2020 and there had been some contact from NRL clubs about his future plans.
But the financial muscle of Wolfpack's billionaire owner, Australian mining magnate David Argyle, and the chance to show off his talent to a new audience was a opportunity he couldn't ignore.
"It's great what Toronto have done and what they're trying to achieve,' Williams said.
"It all lined up and... I thought it was just meant to be."
Williams will head back to Sydney this weekend for a month-long fitness camp to get his body adjusted to rugby league again five years after completing his second season with the Roosters.
He'll then join up with his new teammates in the north of England after Christmas ahead of the new season on February 2.
The Wolfpack base themselves in Manchester for the opening weeks of the campaign with the weather in Toronto at the time of the year unsuitable for outdoor sports.
The players then switch to their Canadian base in April which is when Williams will be joined by his family.
"I made contact with a couple of the Australian players (at Toronto) and by all accounts it's different and there are challenges," he said.
"But I've always had challenges in my journey, so this is nothing I'm not used to.
"Overall what they're trying to achieve on and off the field is something special.
"Instead of looking at the challenge and thinking 'what if I fail', it's 'what if we succeed and I am part of that'."