According to the Srimad Bhagavat Mahapurana, when will Kali Yuga end and Satya Yuga begin?

Yadā candraś ca sūryaś ca tathā tiṣyabṛhaspatī।
Ekarāśau sameṣyanti bhaviṣyati tadā kṛtam॥

- Shrimad Bhagwat Mahapuran (12.2.24)

When the Moon, Sun, and Jupiter enter the first part together of Pushya Nakshatra and come to the same zodiac sign at the same time, that is when Satyayug will commence.

According to astrological calculations, during the 5127 years of Kaliyug, the Sapta Rishis visited Pushya Nakshatra twice, but this astronomical event happened only on 1st August 1943. Hence, it is clear that the Satyayug era started on 1st August 1943.

Just like any construction takes a lot of time to be built, and it takes some time to destroy it as well, similarly, this Kaliyug took 5000 years to be built and it may take 70-80 years to be destroyed.