Even assuming things remain quiet on the Western front and Austria can devote all its energies to fighting the Turks I'm not sure that they could actually make it to Constantinople. The war became more difficult as the Imperial armies invaded into the heart of Rumelia and Austria had chronic problems of command. In order to raise forces from among the German princes of the HRE Leopold was constantly forced to grant one of them command leading to dangerous rivalries and ineffective leadership (Charles of Lorraine vs Max Emmanuel of Bavaria, the inept command of Augustus of Saxony).
It's also worth considering what the Austrian position actually was at the high point OTL. While they were able to take Nis and penetrate deep into Macedonia they didn't really ever hold any territory beyond northern Serbia. Piccolomini's campaigns may have captured some important cities (Skopje, Prizren) but he never secured them or expanded the area under effective Austrian control. The whole campaign was more of a diversionary tactic to keep the Ottomans from moving against Belgrade. Also the Ottomans still held a number of important cities in Hungary as the Austrians moved directly south from Budapest to Petrovaradin and then into Serbia. So Temesvar, for example, was never taken nor was anything in Bosnia.
Assuming the Austrians have more forces to dedicate to campaigns in the 1690s likely their forces will be broken up so that commands can be shared and the Princes appeased with command of their own campaigns. So secondary armies will probably focus on securing Bosnia and the rump of Ottoman controlled Hungary beyond the Tisza while a reinforced main army focuses on a slower (than OTL) but more deliberate reconquest of Serbia. But at a certain point I think enthusiasm will wane. The Spanish Succession can't be put off past the death of Charles II so problems will eventually arise in the west but more importantly I think the German princes will slowly start to pull back their support. As the War moves from defending Germany/Christendom to liberating Hungary (and occupied border country from whence the Turks invade Germany) to essentially conquering new territories for Austria some of the Princes are going to start to reconsider participation.
I think Austria probably considers a peace with the Ottomans that gains it control of Serbia, Bosnia, Kosovo, probably part of Albania and part of Macedonia and maybe some of what is now Bulgaria (Vidin at least). The Ottomans also renounce overlordship of Wallachia, Moldavia and Transylvania. Probably Transylvania follows a similar trajectory to OTL with Leopold refusing a successor to Michael Apafi instead incorporating Transylvania into reconquered Hungary but the other two probably retain autonomy. Moldavia certainly would as it would probably be conceded as within the Polish sphere. I don't think Sobieski would ever be able to conquer Moldavia before his death. Then Augustus is probably still elected King of Poland. If he focused all Saxony forces (not needing to make contributions to Austria if other German princes are not needed in the West) he could perhaps take the Turkish held Black Sea coast between the Dniester and the Dnieper by capturing Ochakov. Perhaps Crimea is induced to Polish vassalage though he'd have to contend with Russian influence in that area so that probably limits Polish gains to west of the Dnieper. Venice maybe is able to retake a bit more territory than OTL, perhaps Valona in Albania or maybe Athens or even Epirus or maybe even Crete depending on where they focus.
So this still leaves a large area of the Balkans, basically southern Macedonia, Thrace, most of Bulgaria and Dobruja under Ottoman control. I can't see France or a western power joining the War. I think its more likely France steps into to force a mediated settlement. France has no interest in letting the Turks collapse and is not well positioned to gain from such a collapse. Maybe Savoy joins if they felt there was some low hanging fruit (an Albania campaign perhaps?) or the other Italian states in support of or in association with Venice. So perhaps an Italian prince gains a small principality in Greece or Albania. But this does leave the Austrians and Russians well positioned to seriously contemplate a Greek project in the 18th century so total collapse could be possible a couple generations down the road if the circumstances are ripe for another joint campaign against the Ottomans.
