Hm, well, Splatoon =/= Smash shouldn't be a hard deduction, but it's pretty easy to tell that the two communities are going to overlap--this website was made by someone who started in Smash afterall, and I think people who are here at this stage of the game (as in before the game is even out) and don't know about competitive Smash are a definite minority.
I doubt we'll have the same problems the Smash community is having because;
- The lead developer is embracing the competitive side
As DubaloSeven stated, Sakurai just.... He's so.... He is very.......
All the time.
He talks about making the game less competitive so it has higher accessibility, something which a game like, say, Skullgirls totally lacks, but doesn't seem to realize that these two things are not mutually exclusive. You can make a game easy to pick up and still have the depth to keep people playing at a high level, look at TF2 or Mario Kart. Sakurai purposely cuts things from the game for these reasons and it really does suffer because of it--but this isn't the thread for that.
- Splatoon doesn't have it's own "Melee"
Even though we have a split between regular and ranked, in the end its all in the same game. People going around saying "Wow I can't believe you don't play ranked! Why even bother!" are going to look like tools and get laughed out of here, which doesn't happen in the Smash community where Melee elitism* runs rampant and starts spats and overall makes the community look bad as well as discourage people from getting into it.
- Splatoon is totally fresh and will have an ironically clean slate
Kind of similar to the above point, but everyone is going to be new at this game--one of the joys of a brand new multiplayer IP is that we're all scrubs, and everyone will be helping everyone get to the top. There won't be a split like in say, Mario Kart, where you have seasoned veterans of the series against people who only played MK7 and MK8 or something like that.
- Splatoon has all kinds of support
Eeeeeeveryone is excited for this game, everyone is gonna play it, and the weak ones will be weeded out eventually, and we'll have a fresh meta for everyone to enjoy. Since the Smash community is also excited for this game, I can see people hosting Splatoon tournies alongside Smash in venues and things like that. Eventually, say, next year or the one after, Splatoon will be an independent community and places like Squidboards will be a buzzing hive of things to do and people to meet!
So to wrap up this long post, Splatoon has a crazy low chance of winding up like Smash did because it's simply not Smash. We should all be free of anxiety and let this new wave wash over us as we sink into the ink of this shining newborn metagame. Viva Splatoon!
*If you're a melee fan im sorry but you really need to see what your community is doing to brawl/smash 4 players. i quit smash because of all the bullying going on and when you take a step back, theres just so much negativity that stems from melee that it ruins the whole smash...dish, i guess. 
