While the original team wasn't really all-male either (Victoria Montessi and Louise Hastings were on the team), I do think they may want to use a more gender neutral name. Besides that I think it ties into the plot of the game. The logo for it is a sun, and we see everyone in their new black-gold outfits with things like Stark's arc reactor, Cap's shield and Nico's Staff of One blazing with radiant flames (also Robbie, Illiyana and Carol too but in places where they already have fire or energy usually so it doesn't stand out as much) and a bunch of glowing runes over them. So I'm guessing the whole team gets powered up by some ancient sun god that the new character ties in with or something, and that's why they're "Suns".