in that there could be some slight clutch slippage involved when a folding prop opens up, especially in a cone type unit - I think that is probably a premise behind cone clutch design to start with - that there will be some "give" in the system under extreme duress. I know there is the damper disc to mitigate drive line shock (as in a hard shift) but there are cases where some clutch slippage is unavoidable. I think slippage is exacerbated by the fact that the cone type clutch is working in an oil bath. On our first Gulf stream crossing we had a dock line (I thought I had secured) wash overboard in constantly breaking waves and wrap around our prop - the prop is in an aperture in the keel-hung rudder, and not usually conducive to sucking a line in, but there it was. In any case, I definitely could feel the clutch slip a bit as the line tightened and rpm dropped. It was night of course and I had quite a tussle getting that line cut off. Our current engine was a used unit and came with a saildrive attached - I had to replace it with a new Kanzki for my configuration, but played with the saildrive on the bench for some time before selling it - I learned quite a lot from it.

I also think you could be right about seeing a lot more saildrives in the future, due mostly to the direction boat design is taking. Right now, however, straight drive set-ups vastly outnumber saildrives of course and thus one does occasionally hear of a sinking due to a worn packing gland ect (most often at the dock). I have heard of saildrive gasket failure as well which tend to happen at sea and can be much more catastrophic in nature - both can be attributed to lack of proper maintenance .