If what I saw in that Splatoon clip is an enhanced port or remaster, then apparently I have no idea what a port is. The character models are different, animate differently, and the entire team introduction is new. The weapons may fall into prior classes but those models are different and new. The map is new, or at least has undergone significant changes on the level of Urchin Underpass' rebuild from the first game. Pants are added, which will change the entire way the current gear-ability system is balanced. The presence of new hairstyles may make other headgear more of an optional thing. No gamepad means no constant map, and means the super-jump mechanic will need to be significantly changed. That's not minor.
If this isn't being called a sequel, then OK, but it sure as hell isn't just a port, enhanced or otherwise. At the very least it appears to be a total rebuild of the original game's concept. Keep in mind how much the development team added to the game in the wake of its initial E3 reveal. A lot was added in less than a year and way more beyond that. The bulk of the team has already had a good amount of time to potentially work on this, and we don't even know whether it's actually a launch title. By next May or June...