The 'fourth density' is the destination of the planet. I wasnt really speaking of those inhabiting it. From what I understand those 'harvestable' to fourth are what one would call spiritually radiant individuals. I dont see a lot of that at this time. I would guess most here will likely repeat 3rd density experience on another planet? However, the majority of this planet is comprised of 3rd density, whose 'calling' would then be to fourth density. It is my understanding it is not possible to go to 5th or higher densities without first going through fourth.
The exceptions would be the 'wanderers' here, whose origins are of higher densities, and there are quite a few of them. Not of course all remembering. There is potential in this scenario to become karmically involved in the forgetting.
There is also that unity experienced during times of transition between incarnate experiences.
I think your statement is true in the sense that ultimately it is a matter of going much farther than fourth density, though in my understanding this doesnt occur in one step.