Williams helped New Zealand win the World Cup in 2011, and the Chiefs last year's Super Rugby title, before honouring a commitment to return to Australian rugby league with the Sydney Roosters this year.
The 27-year-old has been in excellent form since returning to the code where he made his name but Rennie said the prospect of helping the All Blacks defend the rugby World Cup in England might help lure him back to the Chiefs.
"We're working pretty hard in that area and we are pretty confident we can maybe lure him back here at some stage," Rennie told the Australian Associated Press.
"He made a real commitment to league and he might be there for a couple of years yet. There's no guarantees about that but he's certainly committed there this year.
"(With 2015) being a World Cup year, hopefully that will be attractive to him."
While Rennie would welcome Williams back with open arms, Canterbury Bulldogs fans are unlikely to roll out the welcome mat when he lines up against their team for the first time on Friday.
Williams controversially walked out on Canterbury 18 months into a five-year contract in 2008 to play rugby union in France with Toulon.
A small group of fans in Canterbury colours held aloft a banner reading "SBW we will never forget" at the Sydney Football Stadium in Williams's first match back last month, and he can expect a hostile reception at the same stadium on Friday.
Passions among Bulldogs fans have been running so high that Canterbury captain Michael Ennis was moved to appeal for calm.
"I wasn't here so I can't comment on what the fans are feeling, but our focus is about winning the game and not Sonny Bill," he said on Tuesday.
"Personally I hope that our fans travel out there and watch a good game of footy and there's nothing silly going on.
"It should be a great game, they are coming off a loss and we need to win. We don't need any distractions from that."