Now on to her headcanons:
Rainy became a reputable coach at Twilight’s school, being in charge of both the cheering squad and the “Air Track” team. (basically a track team, but only for fliers)
Rainbow eloped, second to marry after Fluttershy, with none other than Zephyr Breeze. It was a bit of an oopsie, and bang, Rainbow was expecting - and it would be a DOUBLE whammy - so they were married quickly. Their family is a little broken, but they all love one another, regardless. Rainbow can be reckless and not the parenting type so she is quick to get on to them, while Zephyr really stepped up to the plate and has become the overprotective father.
Dash lost all her laziness after the twins came into her life. No time to nap when there are diapers to change, and children to feed.
Rainbow is still highly competitive. She is known for angry fits after lost games. However, she is one of the best coaches in Equestria.
Rainbow annually flies with the Wonderbolts non-competitively and anytime she is invited for a show. Whichever team she has that semester for Twilight’s school, they all get to come with her and watch. Rainbow makes it an effort to also visit Applebloom’s camp for aspiring fliers.
Dash isn’t bringing home all the bacon, and neither is Zeph - they are kinda poor. Luckily, Flutters and Applejack help out anytime Rainy needs a hand, er, hoof.