We understand that since Mordor is in the title of the game, the game would be set in Mordor itself but fans of the Middle Earth universe are hoping that they will be able to get out of Mordor and travel to some other places in Middle Earth in the next game.
The fact now is that Monolith has not confirmed that they are working on the sequel to the game but a lot of people seems to believe that they are based on the resume that was leaked earlier this year. The game Shadow of Mordor 2 was listed in the resume of a stunt actress.
While we too would like to go to some of the iconic places in Middle Earth before the the Fellowship of the Ring event start, we will only want to see it happen if it made sense in the story.
Other are also hoping that Monolith would keep the Nemesis system and add a few more features.