Ascension and enlightenment have often been seen as descriptive terms of this thing that's happening right now. These words have at times been used indiscriminately and have been interchanged randomly. In my understanding, from my point of view, they describe two different things that are in interaction with each other, but are not identical. If a person was reaching enlightenment whilst in the paradigm of duality he or she was also ascending, by proxy so to speak. Their vibratory frequency would increase because of their endeavors, their seeking that culminated in finally reaching enlightenment. So in my understanding, if a person reaches enlightenment, they ascend (increase their frequency). However, the reverse is not necessarily true.
Today we see, feel and learn through the myths and prophecies that the frequency of our biosphere is increasing in speed. The Earth is playing a new tune, that is called ascension. People living on Earth can hold their own lower 3D frequency, or decide to move along with the Earth's ascension process and increase their own frequency in their own personal process of ascension. This is a wonderful thing and will bring new ways of perceiving the world around us. It does however not mean, that automatically everyone who has increased their frequency is now all of a sudden becoming enlightened.
What I can see is that the one thing that keeps humans from being enlightened in the first place is the veil of forgetfulness. With the increase in frequency, this veil's density is decreasing, thus it becomes more and more permeable. The veil therefore doesn't cover up who we are as tightly as it used to and we are more able to remember. This thinner, more permeable veil in the higher frequencies will thus facilitate the quest for enlightenment for any true seeker considerably, and we may find waves of people entering the state of enlightenment in the new, less dense, ascended world. That means that enlightenment is just easier to come by while we live within higher frequencies, but it is also still allowed to choose not to seek enlightenment after we have reached the next dimension. It is possible to live with adjusted "ascended" energy vibrations, experience states oneness and have greater consciousness because of the higher frequencies, yet still remain largely unaware of our true nature, i.e. be unenlightened and that too is in perfect Divine order.