While most A380's do not have a seat infront of 81A/K some newer ones do in fact have a seat infront of 81A/K i.e. 80A/K. This was the case on a recent DXB-DFW flight which got switched from an aircraft without the seats infront to A6-EOL which did have 80A/K (luckily I upgraded so wasn't a problem for me). Best advice is get to the airport as early as you can and request 68A/K.