I assume we're talking about opups here and not same-day mileage upgrades? If mileage, theoretically it's possible as long as there are enough unsold seats. If you're hoping for an opup x4 -- I'm sure one or two other FTers have probably hit the jackpot that way, but if it were me I would not be getting excited about the prospect of an opup in this circumstance, and instead would focus on getting excited about a trip with my family.