We have Gervinho, and have Carlos Vela fit and back as a solid squad option. Keep in mind that we still have Arshavin, Chamakh, Van Persie, Walcott, and Cesc is still here. We never had problems scoring goals, and Nasri was average for 3 years except for 6 months of last season.
Arshavin in his self admittedly 'bad' season last year scored 10 goals and 18 assists. Chamakh scored 11 goals and 8 assists. One of them will step up and probably double their output in Nasri's absence, and Gervinho is a much more direct player than Nasri (scored 15 goals last season) and will make a big impact with us.
What I've said time and time again, is that what loses us titles is our injury prone and terrible defence. Vermaelen is back and a world class defender, but how long can he stay fit? He needs one of Cahill, Jagielka, or Samba as a partner or we're going to lose out on all titles again. Wenger knows what he needs to get, but keeping Nasri for another season would be one less problem to think about.