I have a feeling we'll see about 6-8 goals each from De Jong, Riviere and Cabella. I quite like the look of Riviere though and think he could maybe hit 10 or 11, but I don't see him setting the league on fire.
That leaves Cisse, Gouffran, Sissoko, Perez and Ferreyra (with anything from Campbell/Armstrong/Vuckic/Obertan/HBA/Aarons/Sammy a bonus) to try and get 20 or so between them - and the bulk of those will probably come from Cisse if he gets fit fast enough. Can't see Sissoko getting more than 4 or 5, the others bar Ferreyra getting 4 or 5 between them and Ferreyra as an unknown quantity.
Our defence just don't ever score goals, so if we get 3 or 4 all season from the defenders (+ Anita, Colback, Tiote and Abeid) then that's probably a shit load more than I'd expect.
tl;dr version: we'll struggle to score a goal a game in the league without a good quality forward coming in.