According to a massive information cache dumped on the message board 4chan, Marvel Cinematic universe will systematically expand to 70+ characters who are likely to appear in Avengers Infinity War movies, this has set off a kind of competition among every comic-book character wanting to get more screen time or seeking a comeback into MCU.The classic comic-book story is unlikely to change much where Thanos first finds out where all the mind gems are, they are in the possession of all the elders of the universe, it’s different in cinematic universe as Vision has a mind gem, but he clearly isn’t an elder of the universe. In Avengers 3, he will assemble all the gems and create an all-powerful Infinity gauntlet, cause a world-wide catastrophe and then in Avengers 4, Avengers and Guardians unite and fight the mad titan.
In the movie Avengers: Age of Ultron, Maximoff siblings were introduced and Peter Maximoff (Quicksilver) was killed in the same film. He was considered to be the most suitable superhero who can be let go without affecting the marvel cinematic universe in a big way. His sister Wanda Maximoff (Scarlett witch) survived the Battle of Sokovia. She is an all-powerful being, hence less disposable.
There is now a speculation that he may be brought back into Avengers Infinity War, as there can be many interesting story elements that can be used for Marvel Phase 4. There can be four concrete ways in which he could return – He could be part of a flashback which reveals an important information about his origin, background etc. Similar plot device was used in Ant-man which featured Howard Stark and Peggy Carter in a flashback. Secondly, he could come in the Scarlett witch vision during times she feels lonely & sad. Thirdly, he may be saved before he was killed through time-travel or lastly he could even be resurrected through an Infinity stone.
Well, we shall wait and see.