The veteran Wales flanker will be 36 by the time the globe's most-prestigious tournament takes place in New Zealand but the performances of a fellow Lion earlier this summer have persuaded him that age should be no barrier to success.
England second row Simon Shaw was one of the stars of this year's 10-match adventure in South Africa, despite being the oldest man in the party.
And the manner in which Shaw performed in the second and third Tests against the Springboks has persuaded Williams that he can produce a similar level of performance in two years time.
''The next World Cup is getting closer and closer," said Williams, who toured with the Lions in 2001, 2005 and 2009.
''And while the game is definitely getting more physical, look at Simon Shaw on the Lions tour this year.
''Shawsy was superb during that trip, so it can still be done."
As well as the example set by Shaw with Britain and Ireland's elite, a previously short-lived retirement is another factor for Williams' desire to continue on through to rugby's showpiece event .
The Cardiff Blues openside called it quits from the international game after the 2007 World Cup when Wales failed to qualify for the knockout stages.
But the call of his country proved too much to resist and Wales coach Warren Gatland persuaded Williams to return to international duty when the New Zealander took over from Gareth Jenkins.
''When you have a brief taste of retirement, as I did, you realise how much you miss it when you don't have it any more.
''My recent shoulder operation was the first major surgery I've had, so I have been fortunate in that sense, and it always helps when the sides you are playing in are going well.
''People want you to stick around then, but if you start losing people start talking about bringing some fresh blood in!''
"I am looked after really well, at the Blues and with Wales...you just keep going!"