According to Advaita Vedanta, this world is just an illusory perception because of avidya of jiva. When jiva realizes that he is brahman, then nothing else exists for him. If all the jivas in the world attain mukti, then does the scripture statements about creation again after pralaya have any meaning. Is there anyone to perceive this illusory creation? Does some other portion of brahman fall under avidya keeping the statements valid?
This question is more or less duplicate of What will happen if all souls inhabiting Earth attain Moksha? , However as the question deals with interpreting scriptural statements about creation according to Advaita, answering the question:
According to Mandukya Karika of Gaudapada (verse 2.32) :
न निरोधो न चोत्पत्तिर्न बद्धो न च साधकः ।
न मुमुक्षुर्न वै मुक्त इत्येषा परमार्थता ॥ ३२ ॥
na nirodho na cotpattirna baddho na ca sādhakaḥ | na mumukṣurna vai mukta ityeṣā paramārthatā || 32 ||
32. There is no dissolution, no birth, none in bondage, none aspiring for wisdom, no seeker of liberation and none liberated. This is the absolute truth.
Touching to the real question: What abot scriptural statements that talk about creation and dissolution if that's not reality. The answer is: Those statements are purposed to explain the non-duality of Brahman with Jiva and Jagat.
मृल्लोहविस्फुलिङ्गाद्यैः सृष्टिर्या चोदितान्यथा ।
उपायः सोऽवताराय नास्ति भेदः कथंचन ॥ १५ ॥
mṛllohavisphuliṅgādyaiḥ sṛṣṭiryā coditānyathā | upāyaḥ so'vatārāya nāsti bhedaḥ kathaṃcana || 15 ||
15. (The scriptural statements regarding) creation as illustrated by examples of earth, iron, sparks, etc., or otherwise, (only) serve the purpose of (ultimately) explaining the unity (of Jīva and Brahman). (Really speaking) multiplicity does not exist in any manner.
I suggest to go through Adi Shankaracharyas Bashya (on these verse) also which raise some objections and answeres them.
Closely related post: Is Moksha a permanent state?
"All the jivas attain mukti" and " creation again after pralaya" together seem to ask that if all the jivas attain mukti, pralaya will come and after that how can we explain creation? First, creation and Liberation has no realmeaning in Advaitavaada and so we have to understand it in Dvaitabhava.
All jivas do not attain mukti simultaneuslly. Sri Krishna says in Gita:
7.3 Among thousands of men a rare one endeavours for perfection. Even of the perfected ones who are diligent, one perchance knows Me in truth.
18.61 O Arjuna, the Lord resides in the region of the heart of all creatures, revolving through Maya all the creatures (as though) mounted on a machine!
So its clear that God, who can alone grant Mukti, goes on getting the people revolving by Maya and so does not want to give Mukti to all. He gives the mukti to only a few people.So long we are in this world with the senses of "I" and "Me", there is no Advaita for us!
Sri Ramakrishna puts it beautifully in Kathamrita (24 May 1884):
This world is Her play..She sants it to continue for some time.
one of a million kites (Ghuri) get cut.(gets liberated).
So all the jivas will never attain mukti simultaneously. Pralaya will come at the point of time determined by God.
After each pralaya, God projects this world out from within by His maya. He is infinite and so is His maya (Gita):
9.7 O son Kunti, all the beings go back at the end of a cycle to My Prakrti. I project them forth again at the beginning of a cycle.
9.8 Keeping My own prakrti under control, I project forth again and again the whole of this multitude of beings which are powerless owing to the influence of (their own) nature. (tr. by #w. Gambhirananda)
In Sri Ramakrishna's words (8 April 1883):
At the time of pralaya,nothing will remain. The Mother Goddess will pick up the seeds of creation and keep with Her. She will take these seeds out again at the time of next creation.
So to be precise, all are controlled by God, Who wants this creation to continue as He gets joy out of it and so He would never grant Mukti to all simultaneously. At the time of Pralaya.He retains the seeds of creation and sows them again as the new world is projected by Him.
As mentioned earlier, according to Advaitavaada, there is no paramarthika existence of Sristi and so of Mukti.So Advaitavad has nothing to do with it.