Let's face it, Elon has great big brass ones in simultaneously taking on SpaceX (!!!) and Tesla (!!!). SpaceX has already become the fastest growing and cheapest launch provider in the world all based on his huge bet with the Falcon 9 after learning the business with Falcon 1. Next year he plans to release Falcon Heavy which will make SpaceX the dominant player in space transportation.
His business plan for Tesla was identical. Test the waters and learn the business with Roadster. Shock the world and fight for competitive parity with the Model S, then go for the jugular with a generation 3 concept to attain market supremacy.
He has repeatedly stated his 3 version philosophy, pointing to software history of programs like Windows.
So yes. The Model S is for all the marbles, and is absolutely a make or break moment for Tesla. If demand crashes after the pre-orders like happened with the Leaf, Tesla is apt to become merger bait for Toyota or Daimler.
Personally though, the Model S looks like typical Elon magic. Any of the vehicles with the 60-85kW batteries look hyper competitive with a large number of conventional models in the class in terms of performance, styling and total cost (and ease) of ownership. Right now I think the worst case for Tesla will get them to Gen 3 even if they don't become profitable. And a believable best case exists where the Model S is the next must have Cabbage Patch Doll.. Or an Ipad for those of you too young to remember real mania.. :P