Would I like to see a third Elvira pin? Sure, but I'd rather someone other than Stern make it. Stern creates decent pins on average, but their past track record concerns me. Talk of quality and code issues aside, Stern has never really impressed me with their designs.
Stern has been perfectly comfortable putting out pins that more or less followed the status quo set in the late 90's/early 2000. They suddenly embraced LCD screens after Jersey Jack/Dutch Pinball started making machines with LCD screens installed.
If there is to be another Elvira machine, it needs to be a true modern machine. Something similar to JJ's "Dialed In!" machine has done allowing smartphone interaction. It still just needs simple and straight forward objectives (ala Scared Stiff), but with something new that sets it aside from all the current machines. Maybe some small playfield cameras so it can show highlights of some of the shots from the game you just played.