What if Hungary (meaning just the Pannonian Basin) had broken away in 1848 and Galicia-Lodomeria likewise became its own Hapsburg Kingdom?
In the Crimean War, might we perhaps see a revival of Poland with a Galician acquisition of the Vistula Land?
Here, Austria is comprised of Cisleithania, Croatia, and Veneto.
Hungary itself will be unstable due to several ethnicities living there. It depends on how Hungary will treat those ethnicities. At the start they need to give them some autonomy or breakaway is imminent. Autonomy as in recognising their language. It will help at the moment.
Austria will be severely weakened. It might be weakened enough to get Austria and Bohemia within Prussian led Germany. Italy will try to snatch Habsburg Italy. At this point it depends on Napoleon III/France to support Austria or let them fall. Supporting/abandoning will have huge consequences on France. Either a Greater Germany as a result or a divided North-South Germany.
Russia is the biggest winner. No Austria that can be a threat to them, only a growing yet weakish Prussia and an unstable Ottoman Empire in the 1840s not strong enough to hold the Russian Armies alone. At this point it also depends on the United Kingdom and France to either back up Prussia, Ottoman Empire AND Galicia against Russian plans for Eastern Europe. And they will have those plans. One can assume Hungary will also be a target of Russia. And if the new independent Galicia gets a Polish identity then Russia has its own problem like the Ottomans had with Serbia.
The Ottomans are also better off in the short term. No Habsburg support for the Obrenovic. But this means more Russia leaning Serbia. But even then, it still depends on Anglo-French support for Istanbul. Hungary might be backed up as well to keep the barrier with Russia as strong as possible. Although I have my doubt if Hungary has any chance of survival if Russia were to intervene against them in favor of pro-Russian minorities (Romanians, Serbs...)