Will at some point the world remain empty?

Vedānta Deśika considers the world to be eternal-though-in-flux, i.e. eternal through change. It is manifested, changes, reabsorbed and is then remanifested and so on forever. But not a single one of this remanifestations is different than the preceding ones. How does this absolute determinism affect the destiny of souls? If the world needs to be the same again and again, will they ever be able to achieve a final liberation? Or will they need to be reborn again and again in order for the world not to change? If the former is the case, and souls achieve a final liberation, could not it be the case that the world, sooner or later, remains empty because everyone has achieved liberation? And, given that the world is eternal, why has this not already happened?
If, by contrast, the latter is the case, and no one (or not everyone) will achieve the final liberation, how can God still be though to be compassionate and ready to help all human beings?
The conundrum seems due to two sorts of problems:

1. 1. The intersection of two levels of discussion, i.e., the ontology of the world and the morality of karman. The two probably should be kept distinct.
2. 2. The connection of two sorts of explanations, i.e., God's intervention in the world on the one hand, and beginninglessness on the other. God seems insignificant, if he has only to guarantee that everything is repeated in exactly the same way, and whimsical if he has things be different each time.

As for the empty world, some suggested that the saṃsāra might appear the same, though being subjectively felt as Vaikuṇṭha by the already liberated souls, who would no longer feel the misery of it and would instead rejoice because they would feel their existence as a chance to serve God. Incidentally, one might suggest that this solution stresses the idea that the two accounts (immutability through cyclical time and grace) regard two different domains (ontology and moral).

All these questions (and some of the answers) have been inspired by Marcus Schmücker's talk on Vedānta Deśika's view of Viṣṇu, on the 24th of May, during the workshop he organised in Vienna on Viṣṇu-Nārāyaṇa.

On Vedānta Deśika, see this post. For more information on the workshop, see this page (a programme is also available, on the up-right corner). On free will, see the corresponding tag and especially this post (on free will and determinism).