There are plenty of experts willing to assess the relative and absolute chances of quakes on those faults - I'm not going to put up half-thought out numbers.

But my best guess would be that the current threat is just the same as it has been on average for the last thousand years on each fault, with the adjustment that recent nearby big earthquake activity raises that risk.

I'm a little surprised that the runs of activity now in Sumatra and in the 1940's in Turkey doesn't suggest to you that earthquakes in a region are more likely when other faults in the area have recently broken than when there has been quiet, as is now the case in southernmost California, with the last major activity even further north on the SAF in 1857.

Personally, I don't think one can logically argue both the unzipping of the Anatolian fault dominates the risk to Istanbul AND that the "overdueness" makes the southern SAF a dodgy place to inhabit.