From the way I look at 'dimension', it is a word used by humans to describe 'level of consciousness'. To other star beings, however, they're not entirely concerning much about this term but to observe how the cosmic beings manifest their resonance with the cosmic entities and hence based on their level of consciousness to further manipulate those entities for the sake of 'balance' or 'imbalance'.
From the way I look at '4D' and '5D', they are, in fact, VERY CLOSE indeed. Beings in both of these dimensions understand very well about how the cosmic energy works but the difference is: Their respective 'agenda' through the use of such cosmic wisdom -- again, for 'balance', or 'imbalance'. This is why Satya stressed very much about their agenda through his vehicle's book called 'The Pleiadian Agenda'.
What Brad Johnson mentioned in his Facebook note here, is in fact not wrong when the negative energy has been too intensively manipulated by 4D's agenda that causing serious polarity imbalance on this planet Earth. In the cosmic point of view, polarity bias, whether extremely negative or positive, will cause polarity imbalance – in the 3D human term, they call it ‘chaos’. However, prior to entering the 5th dimensional realm of consciousness, it is not possible for humanity to neutralize the extreme negative energy with neutral energy. Instead, it has to be neutralized by an equal amount of positive energy to ensure its effectiveness of balancing. This is therefore prior to the ascension to 5th density, 4th density of positive energy will become inevitable. However, upon neutralization and when the planet Earth has returned back to its harmonic state of balance, humanity will begin to enter into the 5th dimensional realm of consciousness.