Rainbow Dash is jumping ahead to the end of Season 3!
The major canon events she'll have undergone are the marriage of Shining Armor and Princess Cadence, the restoration of the Crystal Empire, the adoption of Scootaloo as her protege, attending the Wonderbolts Academy, the reformation of Discord, and Twilight's ascension to being an alicorn.
Though still a daredevil speedster, she has demonstrated that she's willing to stand up for her principles -- to the point that she gave up on her dream of joining the Wonderbolts when it seemed that organization approved of recklessness that endangered others. She also demonstrated a heartwarming willingness to adopt a younger protege as a little sister, and a dedication to getting the Crystal Empire something she herself had lost when she was young. All in all, Rainbow Dash has matured a little, become a little more patient and a little more understanding... but just a little.
CANON UPDATE
The major canon events she'll have undergone are the marriage of Shining Armor and Princess Cadence, the restoration of the Crystal Empire, the adoption of Scootaloo as her protege, attending the Wonderbolts Academy, the reformation of Discord, and Twilight's ascension to being an alicorn.
Though still a daredevil speedster, she has demonstrated that she's willing to stand up for her principles -- to the point that she gave up on her dream of joining the Wonderbolts when it seemed that organization approved of recklessness that endangered others. She also demonstrated a heartwarming willingness to adopt a younger protege as a little sister, and a dedication to getting the Crystal Empire something she herself had lost when she was young. All in all, Rainbow Dash has matured a little, become a little more patient and a little more understanding... but just a little.
Also she writes self-insert fanfiction now.