The way the warranty is phrased is ambiguous enough that it's more likely than not that you will see court cases. If someone has 70% after 4 years/100 000 miles, that would be more degradation than one would expect, but is the battery defective?
What about the Model S taxis? A taxi can travel more than 500 000 miles in 8 years. If the battery dies before 8 years have passed, will Tesla say "The Battery, like all lithium-ion batteries, will experience gradual energy or power loss with time and use. Loss of Battery energy or power over time or due to or resulting from Battery usage, is NOT covered". Technically, they're not saying that the battery must have any energy storage capacity left... I think Tesla has really dropped the ball on the battery warranty terms. Even if Tesla is the nicest company in the world and consideres basically everything a defect to be replaced under warranty, and there's not a single issue with a single Model S battery, anyway, the warranty terms are pretty bad. They will draw a lot of negative attention, just as the Nissan Leaf warranty has drawn a lot of negative attention. (The Nissan Leaf warranty has drawn a lot of negative publicity here in Norway, at least.)
If Tesla wants to replace every fossil car with an electric car, they need to be focusing on important stuff like battery degradation, not trivial stuff like rear seat lighting and whatnot. Actually, the way Tesla has (not) handled the warranty issue makes me nervous to buy a Tesla. It seems more and more like a conscious evasion, and that they're hoping no one will notice that the warranty terms are such that you will get a new battery under warranty if, and only if, Tesla is in the mood to give you a new battery. If battery degradation is for every Model S battery greater than expected over time (something you can't quickly replicate in a lab), Tesla will back slowly away from the Model S and say "battery degradation is to be expected", and then you're out of luck. If you thought you were investing in a car that would provide you for transportation for many years, well, you were wrong.