First of all OTL, everything was militarily in Prussia's favor so how would you see Austria winning? A speedy intervention by France or Russia? Also, it would depend a lot on how decisive that victory was.
Ah, the only thing working in Prussia's favour in the Battle of Sadowa was the fact that they had breech-loaders, as opposed to the Austrian muzzle-loaders. The Austrians had better artillery, superior cavalry and, to top it all of, the Prussian needler was ludicrously short-ranged due to issues with the seals that tended to expel hot gas when fired (meaning Prussian troops did a lot of firing from the hip).
The Austrians, granted, played straight into Prussian hands by going for a close-range encounter, despite their rifles generally having a distinct advantage at range (even if at a lower rate of fire).
So, let's say the Austrians are victorious by not being idiots, the Prussian army in Bohemia is as good as lost. They need to retreat, over the mountains across territory they'd already pillaged for supplies ... while being pursued and harassed by Austrian troops.
Ultimately, even in a status quo peace, Prussia is in deep trouble. They'd left the German Confederation prior to the war and you can bet Austria wasn't going to let them back in, which is not likely to make the German nationalists happy. Prussia literally gambled everything on winning the Austro-Prussian war.
Napoloeon III is likely to intervene as he planned, so you'd likely see Prussia continue existing. Depending on the aftermath of Sadowa, you might see Prussia stripped of some choice bits of land (Silesia, for one, it was a major Austrian goal; Saxony was angling for it's Napoleonic War borders; not sure about the Prussian Rhenish territories, Napoleon wanted to grab bits around the Saar and towards the Rhine, which he might be able to walk away with), which, incidentally, have a majority of Prussian industry.