My 9-hour flight to LHR is in 3 days. Paid for PE and tried to figure out if I can spend my Avios to upgrade to Business.

There's no availability showing for this Friday flight. However, when I check cash price, there are still 3 seats left to be purchased.

I was also checking for the return flight, and there are at least 9 seats in Business that can be purchased with cash, but 0 available for point redemption or upgrade.

Will BA release more seats for redemption/upgrade on the last day so I can still hope for one?