There is little reason to suppose that once the supramental manifestation takes place, that evolution will at that point come to a halt. Humanity has been locked into the idea that the mental evolution was the final phase, and it is now seen that this is just a transitional phase. With the supermind we can expect substantial changes both for individuals and the society as a whole, just as the advent of mind caused substantial changes from the previous status quo. There are likely further levels of consciousness beyond even the Supermind. Yet this is still focused primarily on evolution on the earth, and limited to the scope of our lives and the status of our world.
Humanity used to believe that the earth was the center of the universe and that everything revolved around us. We still maintain the egocentric viewpoint with respect to our own existence, while we at least now acknowledge that, despite our perceptions and habits of thought, the earth actually is part of a solar system and revolves around the sun, and that our solar system is part of the Milky Way galaxy, which is just one galaxy moving through the universe, which is just one universe among many.
We cannot assume therefore that the entire meaning and significance of existence are fixated on the evolutionary development over time of life on earth. It is, however, at this point, premature to speculate about these larger issues, as our current limited mental development simply cannot perceive nor understand these larger frames of existence.
There remains much to be done to prepare Matter, Life and Mind for the advent of a new higher power of consciousness and its impact on these terms of existence. The questions surrounding anything beyond are, at this point, purely speculative. Our focus, at this time, must be to bring about the needed development of mind-life-body to accommodate the next phase and from there, we will obviously be able to perceive and begin to respond to the stages beyond.
Sri Aurobindo writes: “There would always remain vistas beyond as the infinite Spirit took up towards higher heights and larger breadths the evolving Nature, in the movement of the liberated being towards the possession of the supreme Reality, the supreme existence, consciousness, beatitude. But of this it would be premature to speak: what has been written is perhaps as much as the human mind as it is now constituted can venture to look forward to and the enlightened thought understand in some measure. These consequences of the Truth-consciousness descending and laying its hold upon Matter would be a sufficient justification of the evolutionary labour. In this upward all-uplifting sweep of the Spirit there could be a simultaneous or consecutive downward sweep of the triumph of a spiritualised Nature all-including, all-transmuting and in it there could occur a glorifying change of Matter and the physical consciousness and physical form and functioning of which we could speak as not only the total but the supreme perfection of the body.”
Sri Aurobindo, The Mind of Light, The Perfection of the Body, pp. 41-42
Sri Aurobindo Studies 
Evolution is a very slow process, in scales of millennia. While an external collosal suprabeing can view it occurring fast enough, the system-internal beings with miniscule lifespans would effectively feel evolution not occurring at all.
Like the huge shape of earth, when viewed from moon, is curved, but when experienced by earthlings walking over short distances from home to say market, even for as large as a few kilometres, seem quite straight enough with nil curvature.
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