Basically there are two types of rankings - the one being the actual rankings according to the total ranking system in use since 1658 and the second one being the race based on performances this year to participate in the Player Championship in Turyn in November 2021.
The Standard ATP Ranking
1 Novak Djokovic 12 133
2 Danill Medvedev 10 780
3 Stefanos Tsisipas 8 350
4 Alexander Sverev 7 760
5 Andrey Rublev 6 130
6 Rafael Nadal 5 815
7 Matteo Berrettini 5 173
8 Dominic Thiem 4 195
9 Roger Federer 3 765
10 Casper Ruud 3 440
11 Felix Auger-Aliasime 3 368
12 Denis Shapovalov 3 310
13 Hubert Hurkacz 3 128
There is no certainty as to what the situation by the end of the year would be. Djokovic played in a few tournaments only this year and his bifg wins in three of the four Master's tournaments and in four clay court tournaments - where he lost in three of those. He did not indicate yet when he is going to play again. If the p[resent pattern continues he will be out of his no 1 ranking before the end of the year.
Rafael Nadal will not play tennis again this year and Federer seem to have gone on a quiet retirement and si likely not to play again this year.
The race to Turin
1 Novak Djokovic 8 370
2 Danill Medvedev 6 380
3 Stefanos Tsitsipas 5 470
4 Alexander Tserev 4 915
5 Andrey Rublev 4 030
6 Matteo Berrettini 3 955
7 Rafael Nadal 2 985
8 Caspar Ruud 2 675
9 Hubert Hurkacz 2 505
10 Felix Auger-Aliassime 2 320
11 Jannik Sinner 2 255
The last tournament was held in November 2020 in London. After years of absence by Djokovic and Nadal - they played in the 2020 tournament in London and both did not do well. both were beaten twice and Djokovic lost to both Medzedev and Thiem. It is uncertain whether Djokovic will in fact play in the Turin tournament
As to Nadal - he ahs already decided to quit playing any tennis this year, If Djokovic do not play there will be a close tussle between Auger-Aliassime and Sinner for the no 8 positiona dn Shapovalov may also come into contention. . .