Edit 2: English post on Splatoon US tumblr
The Japanese Splatoon twitter account posted some info about how the online functionalities will work in Splatoon 2:
https://twitter.com/SplatoonJP/status/826766508487380993
https://twitter.com/SplatoonJP/status/826766755523547138
Thanks KtSlime for the translation:
Random matchmaking will probably work without the smartphone app.
Edit: added another translation
_____We've received a report that Splatoon 2 will be compatible with an upcoming app for smart devices that enhances online play. This app will link with the game and allow you to set a play appointment with your friends and teammates invited through your social media accounts. It also lets you match up with them directly in the game and voice chat with them too.
For example, during a Private Battle, you can voice chat with all of the connected friends when you divide into teams, but once teams are set, voice chat is switched to communication only between teammates in the same team. Also, you cannot communicate with random Inklings you don't know.
The Japanese Splatoon twitter account posted some info about how the online functionalities will work in Splatoon 2:
https://twitter.com/SplatoonJP/status/826766508487380993
https://twitter.com/SplatoonJP/status/826766755523547138
Thanks KtSlime for the translation:
It's kind of a rough translation (with some liberties) but here you go.
Splatoon 2 (will use) the "Online Lobby and Voice Chat" Smartphone app for Nintendo Switch.
This app, linking with the game, is the (tool) to do matching in the game, and meeting up with friends invited by SNS and (friend list?), it even does voice chat.
Voice chat is also linked to the game.
For instance, in a private match, you can chat with all rendezvousing members before splitting into teams, and then the conversation changes to only speaking to those on the same team.
Now you can't converse with someone you don't know.
Random matchmaking will probably work without the smartphone app.
Edit: added another translation
『スプラトゥーン2』は、Nintendo Switchのスマートフォン向け「オンラインロビー&ボイスチャット」アプリに対応する。
このアプリはゲームと連動しており、フレンドやSNSで招待した仲間と待ち合わせて、そのままゲームでマッチングし、ボイスチャットもできる仕組みだ。
Splatoon 2 works in conjunction with the Switch's "online lobby and voice chat" app. The app, working in conjunction with the game, allows players to add people in their friends' list or from social media and make use of voice chat and matching features.
ボイスチャットもゲームと連動している。 例えば、プライベートマッチでは、チーム分けする前は待ち合わせた仲間全員と会話ができるが、チーム分け後は同じチーム内だけの会話に切り替わる。 なお、見知らぬ誰かと会話することはできない。
The voice chat's functionality is also linked to the game itself. For example, when starting a private match, everyone is involved in the same chat but as soon as you are split into teams you're separated into your team's private chat. You cannot chat with anyone that you do not know.
/rushjob
Hopefully the language here is a little easier to follow.