Turns out, we could be seeing a ring on Nicole's finger by the end of the year.
After Lewis, 29, secured the world title at the Abu Dhabi Grand Prix on Sunday, odds on him popping the question to the 36-year-old Pussycat Dolls singer have shot up.
Nicole watched her boyfriend drive to victory and joined Hamilton's friends and family to celebrate the good news.
"I'm so happy for him," she told the BBC after the race.
"To me he is always the world champion and I'm just really proud of his dedication and his heart and his sacrifice this year and it's really paid off."
TV cameras showed Nicole rushing to kiss her boyfriend - through his helmet - at the side of the track after Sunday's win (cute!). It's this romantic moment that has sparked the engagement speculation.
OK! magazine reports odds of the couple announcing their engagement by the end of the year stand at 5/1 while the odds of them tying the knot before 2016 are now at 6/1.
"Nicole was as emotional as Lewis was at the end of the Abu Dhabi GP and after a very on off relationship it seems as if they are very firmly on at the moment and a wedding may be on the cards soon," a spokesperson for William Hill told the magazine.
It's not the first time the couple have been rumoured to be taking the next step in their relationship, though.
Nicole's father Alfonso Valiente revealed the pair were engaged in an interview with the Mail on Sunday in 2011.
And after they split up briefly in July 2013, a friend of Lewis' told the Mirror they are together for good this time.
"During the time Lewis and Nicole spent apart, he was absolutely distraught and he said that if he ever got her back he would never let her go," the source said.
"He adores Nicole. They are so in love. Their circle of friends think that now they're back together they will be married within months."
Are those wedding bells we hear?
More of Nicole below: