There are a lot of speculations that the "super secret scene" is indeed Sawyer showing up on mainland in the future. The writers themselves, in some interviews, have mentioned how after this finale there could come a time where the story won't need flashes anmore.
I doubt it though, because 1) if Sawyer or all the people we think were left behind would show up in the future, it would be a repeat of last year WTF; and 2) even if it were only Sawyer showing up in the future, and for a one time thing 8maybe to introduce the Orchid as a time travel machine or something like that), didn't they already used the trick with Ben in 4x09?