The vote by the NBA Board of Governors has been pushed back beyond Friday, the league confirmed Tuesday.
McGinn said he was informed Monday by commissioner David Stern the vote on the very complex deal would instead happen in the next week or two.
The news comes as McGinn announced he reached agreements with Chris Hansen's investor group over the use of KeyArena as a temporary home for the Seattle Sonics, should the team return to the Northwest.
Hansen agreed to pay the city $2 million in annual use fees, with the city also potentially receiving additional money if ticket sales are strong. An additional $750,000 would be paid annually to Seattle if an NHL hockey team is brought to KeyArena.
Hansen's group also commits to making $3 million in upgrades to the Key, including better seating, improving locker rooms and club facilities, better TV broadcast infrastructure and sprucing up the concourses with flat screen TVs, kitchen upgrades and improving suites.
"Chris Hansen and his team want to make sure it's a great fan experience. We wanted to make sure we protected the city's budget," McGinn said.
The deal also assures all city employees who work at the Key will remain so with their labor costs reimbursed by Hansen's group. Hansen also agrees to abide by any and all union contracts.
If the deal is approved by the Seattle City Council, Hansen's ArenaCo will assume operations of KeyArena at the beginning of July 2013 and remain in charge through the duration of NBA basketball being played at the facility.
"This agreement increases revenue to the City from KeyArena, realizes a great private investment in a Seattle landmark and will add to the vibrancy of the Seattle Center by helping bring the Sonics home," McGinn said in a statement released to the press.
Meanwhile in Sacramento, Mayor Kevin Johnson brought together members of the local investment team to make one final public relations push for the capital city's bid.
Saying the group had "an amazing last two days," Johnson said their best and final offer is ready to go. "We want to revitalize this community, we want to globalize our franchise, and we want to transform our team," he said.
The NBA said there will only be one public news conference this week related to the Board of Governors. That is expected to happen Friday afternoon. No members of either city's delegation is invited to attend the meetings.