In X-Men 3: The Last Stand, after Magneto rescues Mystique and frees a bunch of other mutants, one of the guards goes to shoot him only for Mystique to protect him, being hit by the Serum Darts that strips her of her mutation and to be left behind by Magneto because she is "no longer one of us". At the end of the film we see Magneto (having been shot and lost his powers) seeming to get them back by slightly moving a metal chess piece.
In X-Men: Days of Future Past we see Magneto again with his powers, confirming what we saw in X-Men 3, and we know that Days of Future Past starts off in the same timeline because it carried on from the The Wolverine post-credits scene where Charles and Magneto recruit Logan and in The Wolverine Logan is still trying to get over him killing Jean in X-Men 3.
Since Magneto got his mutation back, do we know if Mystique got hers back from after being shot? Or if the injection Rogue got ultimately wore off (since the serum that was created from Leech).