Would you just fall of the edge? Or is there more land behind Antartica? Explain.
Aaaaaand you just stumped every FE on the page. Even Tom Bishop says 'Unknown'. HA!
"We don't know" is a perfectly acceptable, honest answer in this case - and we should take the FE'ers at their word on this one. The reason (it is claimed) that this isn't known by the general public is that NASA and the UN (and, by implication, a hell of a lot of other organizations) have suppressed the knowledge. So there is an explanation that says "We don't know" - and backup to explain why we don't know. That is an intellectually honest position.
The only problem with "We don't know" answers is that if you do that too often, you end up with a theory of the universe that has more holes than it has substance...and if another theory comes along (Concave Earth Theory maybe - or RET for sure) that has only a few tiny, insignificant holes - then rational, thinking beings should go with the theory with fewer unknowns.