Bleach: Thousand-Year Blood War cour 4 has finally cleared up one of the biggest uncertainties in the fandom over the past few months. New reports confirm how many episodes would be part of the final stretch of Tite Kubo’s saga as rumors continued to surface online.
A social media post claimed that the last arc, “The Calamity,” has only 10 episodes. No official announcement has been made to confirm this claim. The Bleach: Thousand-Year Blood War cour 4 was originally supposed to be part of a total of 52 episodes for four cours, with each of the previous cours consisting of either 13 or 14 episodes.

However, there has been no official announcement backing up the 10-episode claim thus far, and the source of the information itself has been identified as a fan-made guide that accepts that its information may not be accurate.
Official messaging points elsewhere. The coverage indicated that the show had 52 episodes planned. Cour 3 surpassed its original 13 episodes, and Cour 4 is said to contain the most anime-original material. This means something like a 10-episode run is likely improbable since more content usually requires more length.
Release date and staff details of Bleach: Thousand-Year Blood War cour 4

Bleach: Thousand-Year Blood War cour 4 is set to premiere on July 25. The season carries the subtitle "The Calamity" and is being directed by Hikaru Murata under Studio Pierrot Films. This marks a shift in directorial credit from earlier cours, though the production studio remains consistent with the rest of the franchise.
Ahead of the television premiere, the first three installments of the series were screened in theaters before being broadcast on television, which gave a chance to see them earlier than others. The Hulu streaming service will provide access to the new episodes in the USA, while Disney+ will be responsible for showing them abroad.
What the extra runtime means for content

Bleach: Thousand-Year Blood War cour 4 will finish adapting all the remaining chapters of the manga, which is about two dozen chapters. Based on the usual implementation speed of the anime, the source material will just be approx. 3–4 episodes in length. This means that in a 13-episode run, there will be lots of room for anime-original content.
As per expectations, that content should include scenes that took place but are not shown in the original manga, and should not follow the totally different plot. Among various options that are being discussed are Uryu Ishida's backstory, Sosuke Aizen's past, further scenes with Arrancars, and some additional scenes, e. g., Sado's combat.
Final verdict
The safest thing to know at present is this: no studio, no accredited Bleach page, and no verified official information states the total number of episodes for Bleach: Thousand-Year Blood War Cour 4 to be 10. The only figure given from an official source at one or the other moment is that the whole story is 52 episodes long.
The public will find out all the necessary information soon. Bleach: Thousand-Year Blood War cour 4 is going to premiere on July 25, and the number of episodes will be calculated with every new episode.