With 80 missions to beat there are new stories that will shed some light on beloved characters, and those that complete the campaign will be able to play as Octolings in multiplayer. (nintendo-insider.com)
Various leakers have said that along with playable Octolings in Splatoon, the Nintendo Switch port of the game will come with more free DLC and more new content, which would likely include new maps, new weapons, and new customization options, along with more game modes (including, according to Nintendo leaker Laura Kate Dale, a 1 v 1 mode intended for when you're using the portable version of the Switch). (segmentnext.com)
Another look at the revamped Octolings for Splatoon 2. (gonintendo.com)