As noted by jja on WaterWar.net, a few upcoming 2018 Nerf Super Soaker model images have been found.
Based on these low-resolution images, the Splash Mouth and Twin Tide appear to be pump-action, but am unclear on the Soakzooka. If I were to guess, the Soakzooka might use a trigger-less small stored-energy system like the 2008 Super Soaker Quick Blast, but this is purely speculation due to the pump shape and lack of a notable trigger (unless that isn’t a pump, but a lever-based trigger). As for why a water blaster with “gatling-gun”-type styling was given a name containing “-zooka” remains to be understood. As for the “Splash Mouth”, it looks like water can be *sloshed* out of a hole in the top (?).
I did stumble across one other name for a possible upcoming 2018 Nerf Super Soaker, the Nerf Super Soaker Zombie Strike Ripstorm, but as there are no images, yet, it remains unclear whether this item will actually be available, yet.
More info on upcoming water blasters as information becomes available. Soak on!