Very interesting topic indeed.
With all the redundancies built into todays modern A/C it's fine to have two pilots up front although this thread questions that but what about the SP ops of any nature?. With all but the coffee urn (&there's more then one anyway in a lot of cases) duplicated there is after all only a 'one heart pilot' at the controls of a SP plane ! Single Engines single pilots, it's all about risk, hence we don't have a large capacity (sure is possible) SE commerical aircraft.
It's obviously rare to see such events (thank God !) so I imagine the A/C of the future will stil have multiple crew but with perhaps less to do.
CW