Floyd Mayweather and Oscar De La Hoya fought way back in 2007. Mayweather won that fight via split decision and a proposed rematch never took place in 2008. De La Hoya then retired in 2009, but we hear is now mulling a return to the ring.
Probably not much chance a second Mayweather-De La Hoya fight would do MayPac numbers, but there are likely still chumps who will line up to spend money on a pay-per-view. Mayweather would LOVE to take their money