I think it is very probable, as long as Austria keeps friendly relations with France. The Italians (Still Kingdom of Sardinia probably) might ally with Prussia in the war of 1866, but then France might intervene on the Austrian side.
Maybe Austria might find an Ausgleich-like solution for Lumbardy-Venetia, but even without, the Habsburgs should easily keep it even if the rest of Italy somehow unites, as long as they keep a friendly relationship with France. Possibly to have this you should avoid Napoleon III, maybe even better would be a surviving Bourbon restoration in France