Actually, I mentioned only the whole of Serbia and Bosnia becoming Austrian in a victorious war 0f 1739. Then, if the alliance between Russia and Austria holds longer, meaning thoughout some additional wars as it did IOTL anyway, the Austrians and Russians might conquer the whole European part of the Ottoman empire in these subsequent wars. Obviously, destroying the Ottoman Empire in 1739 was out of reach. However, I once read that the court in Vienna expected major gains from this war.
If the Austrians join every Russish-Turkish war and win, and somehow Prussian interference is butterflied away, it is absolutely realistic that by 1806 the european part of the Ottoman empire is reduced to Thracia. Now if ITTL Austria and Russia attack the Ottomans, they could easily conquer Konstantinople. Now that would be interesting how Britain and Napoleon react to that.