I actually ended up creating an account just to answer this thread.
Don't bother calling me a fanboy, I'll laugh.
To the OP:
An encyclopedia is a bizarre place to look for the definition of a word, I suggest a dictionary myself. Sequel is defined as follows.
a literary work, movie, etc., that is complete in itself but continues the narrative of a preceding work.
Now, in keeping with this definition of the word, Crysis 2 is in fact a sequel, regardless of anyone's personal opinion as far as step up/step down.
Crysis 1, in single player, which would be where the sequel part comes in, was a series of tactical environments within an overall strategic theater of operations.
Crysis 2, in single player, promises to be the same thing, in a different location, with a different antagonist, in keeping with continuing the narrative.
Now as far as multiplayer is concerned, I fail to see how it is inappropriate at all to make the game modes coherent to the plot of the single player game. In a small scale tactical urban environment, large force on force is a surefire way to have constant friendly fire incidents.
Something the Crysis Wars gameplay advocates seem to repeatedly forget is that the title of the game being released is NOT Crysis Wars 2 or Crysis Warhead 2. Crysis Warhead and, to a lesser extent, Crysis Wars, specifically on the large maps, with vehicles, were NOT the same gameplay as Crysis. They were an entirely different experience.
Expecting a Warhead clone with a new engine would be the "Step down" that everyone is accusing Crytek of. Instead of pushing into a NEW environment in an appropriate manner, they would be doing the same OLD thing.