There is no question that manufacturers publicize their vehicles as being fit for service for periods, not specified, but obviously more than the warranty states. If they are going to be responsible for only the warranty period, then they should say nothing to even hint that the car will be servicable longer than that. They can't have it both ways.
We don't know if maintenance etc. was considered in this court case. Without knowing the full details of this case, I'd think the manufacturer bears more responsibility if the problem can be pinned down as a design or manufacturing defect, and even more responsibility if it's also a safety hazard.
Also bearing on the matter is the seller. If, for instance, it was a certified used car from a same-brand dealership, then the brand should have more responsibility. The last car I bought was from a same-brand dealership, and I asked for and got a copy of their internal service department inspection checklist. I felt I could use that if I experienced an expensive problem after the stated 30-day warranty period.
I don't think this will result in "floodgates opening". Even a small claims case is a fairly traumatic experience for most people, and you can't be unaware that you might end up getting nothing and having to pay a large corporation's legal costs.
If the floodgates did open, then what is the effect? Well, cars will cost a little more because the manufacturers have to support them longer. This would be tempered by the defect/safety angles mentioned above. I doubt rusted mufflers will be covered. On the other hand, maybe silly design errors would be less common and new models would see improved testing. So even if cars cost a little more, they'd hold up better. In the long run, premature failure is a form of waste and everyone would benefit from reduced waste.
Probably the most serious side effect would be loss of sales of extended warranties. So it goes.
As for me, the failure of the electric power steering boost on my Escape certainly has court action in the back of my mind. Especially since it's a known problem and a safety hazard -- and cost a lot to fix.
