The breakup of Austria-Hungary was as much imposed on the country by the Allies as something that the subject nationalities wanted themselves. Yes, many wanted it, but Trianon was really as much about punishing Austria and pushing for a very Wilsonian (and thus half-nonsensical) idea of national self-determination (and democracy, because god forbid Hungary get to keep the Hapsburgs like they wanted). And giving France their circle of allies in the region. Yugoslavia was not really something most non-Serbs wanted, or at least not in the way Serbia got it, but because the Serbs were recast as the good guys of the Balkans by the Entente, they got their wish list from Santa, even at the expense of the Italians.
Austria had a lot of problems after 4 years of expensive war, but the Hapsburgs were now free of Franz Joseph and his stodgy conservatism, so I'd say Austria has an even chance of doing much better now, all said and done. The real trick will be slapping the Hungarians hard enough to get them to accept reforms, but if the returning PoWs try for revolution, Austria may hold any assistance hostage to renegotiation of things.
They should anyway.