I'm not entirely sure to be honest. I think that I wouldn't care at that point, me being dead and all. If I had a choice, I'd rather be buried genderless if nobody knew at the time, but if people knew I would rather be buried as my true gender.
On a related note, regardless of what gender I'm buried as, I want my casket to be dropped out of a flying plane while on fire directly into my funeral plot, without the fire burning my body.