Splatoon's popularity has not diminished over the last year. Although Nintendo had claimed to be cutting off additional content updates back in January, since then a set of eight weapons, called Sheldon's Picks after the in-game arms dealer, was nevertheless released to pleasantly surprised inklings in April. Now, a second set of eight comprising Volume 2 of Sheldon's Picks is planned for the first week of June. Tell us again about no new updates?
Actually, producer of Splatoon, Hisashi Nogami had apparently hinted, at a tournament in Japan, that efforts might still be underway to bring new updates to the game. Translators on NeoGaf interpreted his words to mean that the may be hoping to continue adding content in some form. It seems they were correct.
It's also technically true that no more content has been released; weapons in Splatoon consist of three aspects: Main, Secondary, and Super. The weapons being let out now are actually just existing ones with new combinations of the existing aspects, such as an old gun with a super previously not matched with it. However, this was how many weapons were differentiated, even when the game was getting new content. The final update before February did contain a new map, Ancho-V Games, so if a new map pack suddenly shows up, then we can say that they've gone back on their word (Not that anyone's really complaining).
The first volume of Sheldon's Picks seems to have focused on lighter weapons, like the Inkbrush and Shooters such as the fan-favorite Splattershot. Again, these weapons were remixed with slight tweaks and paired up with secondary weapons never before put together. Judging from the "box art" on the release post for the upcoming second volume, the heavy side of the ink-spreading industry will now take center stage. Splatling guns, Rollers, and the powerful Blaster will all get some new partners next week. Light automatic inkers are still represented, with a new variant on the N-Zap seeming to make an appearance as well. You'd need a calculator to count how many combinations all the weapon options in Splatoon can make, so let's keep hoping new updates keep sneaking in.