If they don't advertise the new content on TV then it would be probably more beneficial to just........release in Sept.

Both Sony AND Microsoft's whole 2015 is very unimpressive really. Yeh we have The Witcher III, Arkham Knight etc have come out/coming soon, I don't particularly count third party titles when it comes to things like this. All we have this year in terms of first party exclusives are The Order(bad-average game), Bloodborne(excellent), Ori(excellent), Halo 5(yet to be seen, should be great but might be rushed), Tomb Raider(much like Halo 5, should be great but seems like it could be rushed) and the next Forza(has gotten a bit stale). I'm probably missing some but both of these consoles are well into their second year. I think Sony are too comfortable in that the console is smashing sales without many exclusives as is and that they have marketing rights to most of the major third party titles anyway(Arkham Knight, MGS5, Star Wars Battlefront and most likely Black Ops 3) and Microsoft are not in the position to left their first party focus a bit late as they did not foresee such a battle. Just my opinion.

Not gonna disagree here, there's a reason why I still don't own any 8th gen consoles. I'm waiting for the Wii U to get a price cut and there is still high price and lack of incentive through software to justify getting either a One or a PS4 yet.
2015 is looking like an overall boring gaming year on consoles for me, I have no interest in Halo or Forza, Bloodborne is not my type of game, Zelda and Uncharted 4 both got pushed back and I'm already set on buying The Witcher 3 for PC (always was).

The highlight of this year for me has been Pillars of Eternity for PC and now I'm looking to buy Serpent in the Staglands and The Witcher 3 next month.

Obviously this was a deliberate and planned move. This is Nintendo we're talking about here. If the game wasn't finished they would not hesitate to delay it, droughts be damned. See practically every other Wii U game ever.

It may be an intentional strategy, but that doesn't make it a good thing.

They definitely need to put more stuff into the game. Splatoon has so much potential, it's mind boggling. It really pains me to see such a brilliant game lack in content. More maps are a given (and already confirmed of course), but there's so much stuff missing: 3- or 4-team matches; Offline versus; Online with 2-4 players on one console (I really want to build a team with my friends and play on one console!); more customization options and additional game modes. The game and its underlying mechanic are so diverse and have so much potential.

I am sorry to say this, but I see this as a desperation attempt to prevent a delay. Other companies do something similar. They have a beta release to distract people from the distant release date (take hearthstone and heroes of the storm for example). Nintendo is just disguising their beta release as a release to distract people from the fact that they released a very very small amount so far this year.

Legend of zelda was delayed, project gaurd and project robot have not seen the light of day, their last really big third party release (project cars) just got delayed or cancelled and kirby was a budget title. This all means splatoon could not have been delayed or they would have received insane backlash.

I personally do not know where this "Nintendo is doing this for longetivity" argument has risen. If that truly was the case, Nintendo themselves would have mentioned it, but not once (either through announcement or interview) have they ever mentioned it. It seems as though people are simply making this up to help Nintendo.

Splatoon is releasing with less than half of the final release content. This cannot have been done deliberately knowing that they were gonna sell the game for $60 in some regions. Why? Because other games like titanfall received backlash for doing something similar.

This, IF they are doing this deliberately, they can at least mention it in their advertisements so as not to mislead customers.

Given the release model for Splatoon includes free updates within weeks of launch, I say the drought is worse.  It stretches Splatoon's influence over the bone dry summer.  If there is a time a release model like this one can work, it's summer where very little releases on any platform.  As for reviewers deducting or not deducting, value is not only judged by amount of content but how satisfying it is.  And also, because free content is coming mere weeks later and is part of Splatoon's release plan, content there at launch isn't held to the same standard as another game with lacking content and paid DLC coming.  In the latter of those, the content needs to stand on its own and validate the purchase.  In Splatoon's case, the launch content only needs to be sufficient for the first month to justify buying at launch.  

I do mind some of the basic features that are missing. A time limit choice. People can't spectate. Friends are never locked to your team. Lack of map vote choice, Online story co-op, can't change loadout while in game, voice chat, Or color choice vote. This can also backfire. People get bored fast. And will eventually move on to something else. So these fixes will become moot to those people. Also, the annoying tv news spam, lagging hub, and character spam text are another sign of rush work.