For more than a year now, Nintendo have been providing frequent updates for their online multiplayer shooter, Splatoon 2. Earlier today, the Nintendo of Europe Twitter page revealed the final new stage, 'Skipper Pavilion', which will be released in October. This means that the final version of the game will have a total of 24 maps, including the 16 added since August last year. That's 8 more than the original Splatoon game's final stage count.
It is possible that this is just the last 'new' stage to be added, and that other maps from Splatoon on Wii U could be added in the future, but it seems unlikely.