I would assume that having a tournament at E3 gives it a higher chance of being a new game. 

But thats a point, last year there was not paid online, and now we know that paid online is coming in September, so Nintendo will most likly launch big online game alongside paid online to push easier paid online.

I really think with live streams and the growing interest in competitive gaming that Nintendo should have a "Nintendo World Championships" every year akin to what Blizzard has done with their titles. It's a lot of fun to watch and with how much easier it is to reach an audience these days I can't imagine it's that expensive to host.

Glad to hear they'll have a competition at E3, at least! That's becoming one of my favorite parts of the event :)

They've introduced new games to competitions in the past, such as Mario Maker or even that Metroid soccer nonsense, so this does not indicate that it's simply a port.

The tournament is on the day of the E3 presentation, so we might not see gameplay until then...

Edit: Maybe not? Nintendo usually does the E3 Direct on Tuesday and if Smash is on Monday, they would have to show it beforehand. I can still totally see them leaving us in the dark until the day of the Direct to do a hype reveal of the gameplay.

Smash Wii U got an invitational aswell though and released in November, so while I still believe Smash 5 will launch in September, this doesn't really make it any more or less likely.

I’m surprised by people saying this is a port.

This invitation further signifying that it’s a brand new game.

This is their big e3 game. I don’t think Nintendo is dumb enough to do that with a port.

I have no doubt that Splatoon 2 will be on Monday and Smash on Tuesday following the presentation, thus yeah we probably wont see the game again until E3. One more direct before then is totally possible, but it'll probably be Mario Tennis specific (or Pokemon if they're really gonna drop it this year). 

There's already tons of footage of Smash for Switch on the internet. Just type in Super Smash Bros. for Wii U. 

That's neat

Really need to improve my skill in Splatoon 2 D: