That would draw the curtain on a glittering international career which has seen Williams establish himself as one of the most potent attacking forces in world rugby.
"If I could play until I was 60 I would but I'm realistic," said Williams.
"Who knows what the future holds? But at the moment this will be my last Six Nations game and it could be quite emotional.
"I'm still enjoying my rugby, I love being in camp and I really don't want to quit Wales.
"But I've got to be realistic and unfortunately I am getting older, we're all getting older we know that.
"We can't go on forever and the thing is there's boys at the moment pushing for places especially in my position.
"If I was a tight-head prop or a loose-head prop I'd play until I was 45!
"But it's getting tougher and tougher, the games are getting harder and harder and I've got to be realistic. I can't go on forever, so realistically this will be my last Six Nations."
The Welsh record try-scorer's double in the 24-6 win against Scotland helped kick-start Wales' Championship campaign and extended his personal try-tally to 53 scores in 79 internationals.
Wales have since recorded wins over Italy and Ireland and travel to France still with a chance of lifting the Six Nations title.
Williams was keep busy with defensive duties and had little opportunity to show is attacking flair against Ireland but he was delighted with Wales recording their third successive triumph.
"It's nice to win of course and three on the trot is very nice, but it was a little bit more special because it was at home and it's been a long time coming really," said Williams.
"It was a good performance by all but wasn't the most spectacular of performances again, but it's nice to see that we can win games without playing to the best of our potential."