Yes I feel like one of "those" posts and I have a feeling the responses are gonna be "It'll be camos!" or "A color book!" (Ugh! I remember that one from BF3), but I'll just post some possibilities and would like to hear yours (Including the two mentioned on top).
I have this unusual feeling it may have to do with the AN-94 because it was seen in the US vs. EU tournament but was nowhere to be seen in Second Assault. I kinda am hoping for it to be the AN 94 or maybe another weapon set (Maybe a BF3 homage with the M417 and whatnot). While I am crossing my fingers for it and it seems probable, it's probably not likely.
Another one that I have this feeling for is, you guessed it, paints and camos. It seems like an impossible amount of paints and camos are left (Unless they release all ten or so of those camos in Final Stand), so I have this feeling it may be the rest or more camos and paints. This seems like the more likely of the two, but I would like to hear some other possibilities.