Is not most of the 'gated' content really 4 person? The only '8' person ones I know of are the ones at the end (that offer tomestones as a reward for helping others). I do not see it as much of a gate right now, and I would hope that there is a continuous influx of people such that one can always find 3 others for these dungeons.
Presently, the only real 'gate' is a few dungeons along the main storyline. Once that is done, then it is Ifrit -> Garuda -> Titan -> Coil. One could call those gates, but one hopefully also sees this as a good way to see if one can progress to the nest challenge.
I think calling it 'gated content' is perhaps a little over emphasis.