Would've been a shock to Christian Europe, certainly. I can imagine a huge force of Imperial troops would retaliate rapidly and probably retake Vienna pretty soon afterward, though it wouldn't be easy. The Imperial Army would likely include troops from all over Europe, as even in England at the time men were worried that soon Ottoman ships would be seen in the Thames.
This kind of loss might even see the armies of western Europe radically reformed, perhaps more nations creating standing armies and those who already had standing armies - as Austria arguably did at a size of 24,500 - to be made larger and more vigorously trained.
Also, I wonder if this would cause a shift in opinions. IOTL the Protestant German troops who helped relieve the Viennese people were verbally abused by Catholics. However, if Vienna is actually taken by the Ottomans, I wonder if the Catholics and Protestants could put aside their hatred for each other and actually work together a little closer...