The lead nominee - with Macklemore & Ryan Lewis - is up for six awards. Timberlake also will be honored with the Michael Jackson Video Vanguard Award, and the anticipation over whether he and his old boy-band cronies will appear together will persist well after the show kicks off Sunday night from Brooklyn.
MTV is officially mum, neither confirming nor denying the rumor, and Joey Fatone has even denied it officially. But 'N Sync debuted a Twitter account Saturday, and the hubbub has overshadowed what will be an all-star lineup at the Barclays Center.
Lady Gaga, Katy Perry and Drake will perform hit singles for the first time, and Robin Thicke, Miley Cyrus and - if the spurned Stephen Colbert is to be believed - Daft Punk square off in a song-of-the-summer competition. But 'N Sync has managed to steal the thunder.
"We're just hoping we're not doing anything after them because anything after 'N Sync this year is going to be irrelevant," One Direction's Harry Styles said.
One Direction didn't give any clues about its role, and MTV has kept many details about the two-hour show under wraps. Taylor Swift, Selena Gomez, A$AP Rocky, Joseph Gordon-Levitt, Jared Leto and last year's host Kevin Hart (MTV has chosen to go without a host this year) are scheduled to participate, and former NBA player Jason Collins, who recently acknowledged he is gay, will introduce Macklemore and Lewis' marriage equality anthem "Same Love."
The Seattle duo is the surprise of the year and is up for six awards, as Timberlake is. The Seattle rap crew has the top song from the first half of 2013, "Thrift Shop" featuring Wanz, one of five songs up for the top honor: video of the year.
Timberlake - who's won seven moonman trophies - has the year's best-selling album, "The 20/20 Experience," and his follow-up "The 20/20 Experience: 2 of 2," is due out in September. His "Mirrors" is up for video of the year. Thicke's "Blurred Lines" featuring T.I. and Pharrell, Bruno Mars' "Locked Out of Heaven" and Swift's "I Knew You Were Trouble" round out the category.
Mars, Cyrus and Thicke have the next-highest number of nominations, with four. Pink and Thirty Seconds to Mars have three apiece.
The show travels to Brooklyn and the brand new Barclays Center for the first time, which should change its vibe. It also will change the iconic moonman trophy. MTV commissioned Brooklyn artist KAWS to redesign the statuette for this year's show.