If Austria regain Silesia it radical changed the entire demography of the Austrian Empire. Let take the last Austrian census the population there increase from 51 to 56 millions. The German population of Austria increases from 12millions to 16 millions, while the Polish population increase from 5 to 6 millions. This ignore the fact that if Austria win in 1866, Austria stay Austria instead of becoming Austria-Hungary. That would mean no Magyarization policy, which would mean at least Bratislava stay a German speaking city, we likely see German majorities in Backa and Banat. The Hungarian Jews would adopt German instead of becoming Hungarian speaking that alone would raise the number of German of the empire by a million people. Budapest itself could very well have ended up German speaking a quarter of the population was Jews. So let’s say that without Magyarization we roughly get a million German more. This bring the Germans of Austria up to 18 million or slightly below one third of the population.