Well, we shall see. Who knows if Pep/Zubi even consider Sakho a serious target.
If Fontas is ready to play 20-30 games next season then we have less of an issue. I presume Milito will leave.
Piqué, Puyol, Abidal and Fontas is okay with Alves, Adriano and Maxwell at the full-back positions but I still feel we would be one defender short. Not least because I'm not sure we can rely on Puyol's fitness as we would need to. Abidal, too, would be getting on in terms of age and has generally (this season aside) been injury prone.
That said, there is of course the possibility of Bartra/Gomez/Muniesa making great leaps in their development.