Johnny K
D) is one of my favorites.
Let's say he gets another twenty-five years.
Given his progress to date, the Byzantines are in pretty good shape. Antioch is probably cemented as under Byzantine rule. The 2nd Crusade is going to be frustrating, but John might handle it better (in terms of foreign relations) than his son. Or not - hard to tell. John was a very different person than Manuel.
John isn't going to be spending significant amounts of effort in Hungary and Serbia, and probably not in Sicily either. That's pretty certain.
If he keeps up his friendliness with the HRE as a way of dealing with Sicily, that's one theater the Byzantines won't be bleeding gold in.
I'd say the Byzantines are looking at a fair amount the plateau by the 1170s - and even at worst the Turks won't be united under either the Seljuks or Danishmends in control of it.
Meanwhile, thanks to him being a savvier spender, the treasury won't be looking as bare.
I'd count this as to the good.
So, that brings us to 1168 or so, and from there it depends on who takes over and what they do. But I think this is the best post-Manzikert possibility.