Without Augustine, Eastern Orthodoxy would be very little affected, but Catholicism would be quite different indeed. Here in the West Augustine is usually seen as the Church Father par excellence, without him its possible that Western theology comes to rely more heavily on the other Great Western Fathers like Hilary, Phoebadius, and Ambrose. This may mean that the filioque clause is avoided, but it's important to remember that most of Augustine's ideas did not come out of a vacuum, and it's entirely possible someone else will propose it. However, without Augustine certain heresies like Pelagianism might be harder to stamp out, and could persist for much longer. This could create division in the Western Church theologically, with the Papacy steadily coming to rely more on Eastern theology if the Eastern Empire can hold on to Rome. The Schism might be avoided, although the absence of Augustine will not change the claims the papacy makes for itself.
In my opinion, no Augustine will mean a lack of a dominant theological paradigm in the West, which will mean that heresies like Arianism and Pelagianism will be able to hold on longer and may even become entrenched in parts of Western Europe. The papacy will probably look to Byzantium for protection, and so long as it's loyal the emperors probably won't mind indulging some of its claims as head of the Church. In my opinion a schism is inevitable, there were just too many contradictory ideas floating around, but it may be more Northern Europe/Mediterranean than East/West.