"The Last of Us" launched back in 2013. Developer Naughty Dog has since been busy with "Uncharted 4: A Thief's End," and it is now speculated that the company will begin working on "The Last of Us 2" once all the post-launch work for "Uncharted 4" has been completed. This may lead to a possible 2021 release.

Speaking to The Frame, creative director Neil Druckmann explained that the writing hasn't been finished yet because writing for a game is done in the middle of production. He explains that this is done because they cannot immediately determine what may or may not work for the game.

This is very different from working on films where the script is completed before the movie begins filming.

Druckmann further explained that work on these kinds of games takes nearly five years. He noted that: "'The Last of Us' took three and a half years. 'Uncharted 4,' during its entire production, took a little over four years."

Back in April, Druckmann also told Games Radar that all of the current prototypes for "The Last of Us 2" have been put on hold as they were set on focusing primarily on the DLCs for "Uncharted 4." Only when the extra content have been completed and launched would the developers return to working on "The Last of Us 2."

Given that DLC packs for the game are still coming out until the end of the year, it is possible that development for "The Last of Us 2" won't begin until 2017. This has fans speculating that the game won't be finished and released until 2021 if the company again takes three to four years to develop and finish the game.

It is important to note that Naughty Dog and Sony have yet to make any announcements regarding "The Last of Us 2," its current production status, and when it may roll out. It is expected to be a PlayStation 4-exclusive title, similar to how the first title was a PS3 and PS4 exclusive.