Assalam-u-Alaikum!
Firstly, we do not have any sources to determine whether Qiyamah will occur in 2500 or 3000 years after the revelation of Quran.
Secondly, the Quran has been revealed as a source of guidance for mankind till Qiyamah. It is neither very long nor too short. Everyone can complete reading it in quite a reasonable time without any inconvenience or hard labor. Why does it matter whether people seek benefit from it for 2500 years or 10,000 years or more? Had it been revealed just for a year, that too would have helped lots of people.