Now recently Quicksilver and Scarlet Witch were first seen held inside two individual cells within the Hydra base Baron Strucker is in who first heard that the Hydra members in SHIELD were exposed and thwarted from using the Helicarriers to kill anyone who poses a threat to them but is confident that he and HYDRA still have a couple more hidden facilities across the globe and when he came upon the wonder twins inside their cells he is sure to use them to regain the upper hand on the heroes by having them join the Avengers, learn about each of them and while they are with them on their mission to battle HYDRA , Strucker would have the twins make sure that the Avengers don't succeed.
After seeing Captain America the Winter Soldier, that HYDRA has been resurrected from extinction by Arnim Zola corrupting people with lies which leads them into becoming HYDRA operatives, we now know why director Joss Whedon doesn't want to make things easier for the heroes and to why Kevin Feige chose Ultron to be the villain instead of going with the Masters of Evil for Avengers 2 because they can't seem to incorporate that many major characters in the movie and all they want is to express stuff certain things in life for many of us to learn as well which and yes Scarlet Witch and Quicksilver are very much likely to survive and return for future Marvel Cinematic films after Age of Ultron because there is much more for Marvel Studios to explore on the Wonder Twins as we speak and surely one movie isn't going to be enough.
For future Marvel Cinematic Films, Quicksilver and Scarlet Witch would appear and cameo in certain films such as Captain America 3, Dr. Strange, Iron Man 4, and Avengers 3.
To learn more stay tuned for more updates on the duo as the Wonder Twins once they come up.