The actress was wearing an understated gold band on her ring finger while toting a bundle of flowers in L.A. on Wednesday – but a source insists, "They are not engaged."
Still, other insiders tell PEOPLE that Kunis and Kutcher – who is separated but not yet divorced from Demi Moore – may have some exciting news to share sooner rather than later.
One source says Kutcher, 35, had talked about popping the question to Kunis around her 30th birthday on Aug. 14. "He knows what they have is amazing and special," says the source, who's in the actor's inner circle. "He's been thinking about proposing for a long time."
Reps have not responded to requests for comment.
"They are clearly very much in love, in tune with each other and so comfortable," an entertainment source close to Kutcher said. "In some ways, it's like they're married already."
But there may be a reason to wait. "Ashton is set on proposing [to Mila]. He really wants to marry her and is so annoyed that there is still the hold up with the divorce," the first source said in July.
Earlier this year, Kutcher's divorce hit a snag when his ex sought spousal support and legal fees, with a source telling PEOPLE at the time, "Demi felt like she had been wronged. She's the one who was forced to end it. She's making a point."
Meanwhile, the former That '70s Show costars – who were first rumored to be dating in April of last year – have been seemingly inseparable.
Their romance has included well-documented PDA and lots of lavish vacationing.
"When Ashton first became a single man via separation, he was eager to date around," another Kutcher source told PEOPLE. "But that has changed since his relationship with Mila has grown and strengthened. His long-term friendship with her became a real romance, and he is very happy."
Splash News Online
Reporting by ELIZABETH LEONARD, LINDA MARX and AILI NAHAS