It was suggested they started using next gen engines for this. So basically what was said (and what I saw in terms of PC gameplay compared to previous games) it is a new engine.

By new engine you mean fish swimming, "destructible environment", and some other crap?

That's not a new engine.
It's simply new things they ADDED.
A new engine would completely change the game.

But I could think of it as a new engine actually.
Knifing, Leaning, and all other animations could be a reason they call it "A new engine".

I personally think it's cool, but still a game I would never buy with my own money. Just one of those repetitive games that you get instantly bored of after 3 months.

COD ghosts will be like PayDay 2. Boring after the first month of owning it.