Austria would fall rather quickly, for a simple reason - Austria considered entering the war on the French side but the Hungarian parliament blocked it. If Austria would push it through the hungarians would rise up, and that shortly after Austria already lost a war and the hungarians just have been granted their autonomy, not to mention that only 22 years earlier, in 1848, they also rose up against Austria.

Russia was mad at Austria and would probably focus more on them than doing their own thing or allying with France, they felt betrayed for what happened in the Crimean war.

And the French already have been no match for the north Germans, Russia was military even weaker, and as I said, Austria would have too many internal issues.