Missing Members: Mary Wilson and Cindy Birdsong, 2000.
Background: To make a long story short, Diana Ross walked away from the Supremes in 1970 and for the next seven years Mary Wilson carried on with other singers before retiring the name. In 2000, a few years after Kiss, the Eagles, Fleetwood Mac and Page & Plant showed just how profitable a reunion could be, a tour was put together called Diana Ross & the Supremes: Return to Love. The only problem was that Mary Wilson and Cindy Birdsong (who replaced original Supreme Florence Ballard in 1967) were offered a tiny percent of the $15 million that Ross was contracted to receive. They balked at the insulting proposal, causing Ross to hit the road with Lynda Lawrence and Sherry Payne, both of whom toured with Mary Wilson as the Supremes in the late 1970s.
Impact on Reunion: The toxic press from the failed negotiations with Wilson and Birdsong completely destroyed the tour. Diana attempted to promote the show on The Today Show and Oprah Winfrey Live, but she couldn't escape constant questions about Wilson and Birdsong. Wilson also took her case to the press and convinced many fans this wasn't a legit reunion in any sense. Some nights Ross & Co. still played to packed houses, but other gigs had huge sections of empty seats. The plug was pulled on the whole thing before it was even halfway over.
Odds of a True Reunion: Close to zero. Mary Wilson and Diana Ross have been feuding for over half a century. They are both 73 years old. They remain active, but Motown acts historically have never made the sort of money on the road that classic-rock acts like the Rolling Stones and the Eagles generate. That means the sort of big-bucks offer they'd need to bury the hatchet just isn't there.