How WORLD WAR Z Originally Ended and why we will never see it

Here is the video where guy explains it in details. From 1 minute mark

https://www.youtube.com/watch?v=R6QgA-ps55I&t=75s

And here is explanation why we will not see it. They didnt do CGI and its just rough material and they would not spend millions to finish it.

Basically in the original ending, after the Israel sequence and the plane crash, Gerry is in Russia, and the storyline of what he finds out at the WHO lab is what he finds in Russia but he applies his theory in a battlefield setting," Forster explained to Movies.com ahead of the film's release this week on Blu-ray. " We never finished that footage because we all agreed after Israel and the plane crash you’re battle fatigued and you really want the movie to be more quiet and you don’t want it to go into another huge combat situation" As Forster points out, some of the Russian battle sequence can be seen in the quick montage at the end of the film, but the complete sequence will never be seen. "I don’t think you’ll ever see the Russia sequence, because we never really finished it; we never spent the money to do the visual effects. Once we shot it and we did a rough cut, everyone agreed that this is too big and too exhausting, it would be better to go a simpler route."

World War Z's original ending, however, began with Lane and Segen (Daniella Kertesz) flying to Moscow where they are immediately drafted into the army being built to fight the zombies. Instead of going to the WHO building, the original ending features a time jump showing a bearded Lane still fighting in Russia during the winter. It's during this time he realizes the zombies move slower in the cold, giving the humans an advantage in these conditions. He's been out of communication with his family this entire time, but he is finally able to speak to his wife, who has secretly had to strike up a relationship with Matthew Fox's World War Z paratrooper to keep her and the kids safe. Later on, Lane, Segen, and a character named Simon begin traveling through Russia to go to the United States and save Lane's family. World War Z's final scene had them arriving in America and storming the country to find his family.

This bleaker ending for World War Z came as a result of the script not being entirely finished when production began on the film. After filming was completed and Marc Forster assembled the first cut of the film though, Paramount executives and Pitt did not like the ending. Those who have seen the early cut of World War Z described the ending (via Vanity Fair) as "abrupt and incoherent," which lines up with the description of the footage that has since been revealed.

In order to fix the ending, Paramount hired Damon Lindelof to rewrite World War Z's script, ordered seven weeks of reshoots, and spent tens of millions of dollars shooting over 40 minutes of the 2-hour blockbuster. Even though all of these changes saw World War Z's budget balloon to over $200 million, it still managed to do fairly well at the box office - earning $540M worldwide.