Well... that was always a thing since X and Y.

It may be a new iteration like how Third Strike to SFIII which even though it's not a new instalment it's still a new game, why I say this is because the game doesn't play the same as S4 and has mechanical changes that change up the entire approach to it.

Well there's a gray line there, because not every new game in a series uses a brand new engine, and the amount of assets they reuse can vary whether it is an enhanced port, or a brand new game.

But if we put it this way. Every new Smash has followed the trend of being on a brand new engine, and distinctly looking and playing different from its predecessor.
Of course that goes hand in hand with the fact that there's only been one per console generation. So it's easier to justify the budget for a new engine in those cases. 
(Take all the versions of Street Fighter 2, for example. It wasn't until the next gen consoles came out that we really got a brand new SF, in SF Alpha. Etc.)
But here we do for the first time have what seems to be a break from that trend when it comes to a console Smash.

And this is what a lot of people wanted, specifically because they still wanted all those amazing guest characters like Cloud that Nintendo spent a lot of money licensing.
So I'd say from the looks of it, it's a super ambitious enhanced port of Smash 4, with obviously all characters from previous games, even some stages, and there are new moves and reworked/re balanced mechanics.

To be honest, I'd much rather they focused their time and resources on all this content, rather than a new engine, and a focus on new stages, etc.

Im sorry, but I dont agree with you at all.I dont see a game being new or old(new game or "iteration") being dependant of what assets it uses and what engine it uses.

Lets agree to disagree on this.

Damnit Nintendo for locking Mew behind that $50 periphial. It's $50 right?

I'll probably get it. Not to buy a $50 mew. I have mew already in my bank, but might be fun playing with it, but if not well then I got a pokeball as a decoration for a shelf I guess.

Where did I bring up assets and engine, point to it in my post.