RE: 3-cyl; I heard they were working on building half a Porsche, just didn't know which half.
Seriously, I've been reading that the spy video/photos are of a Speedster/Spyder model which will weigh 200 lbs less because of the removal of the elec/mech operating roof. Plus it will get an additional 10 hp over the "S" model.
I think that an all electric Porsche will hit the show rooms long before a 3-cyl or Diesel model.
Saying that, a turbo 4 cyl inline costing 10k less sounds like a good marketing move.
Half the buyers are women, right? I'm sure at least half the buyers will not care what's under the hood as long as it says Porsche.