Cydia doesn't count because Apple keeps blocking holes which allow jailbreaking, so with new devices, there can be quite a long time period before you can get back into Cydia.

The jailbreak ruling wasn't from the Supreme Court, it was from the US copyright office, which found that jailbreaking a smartphone was a legitimate exception to DMCA prohibitions on using technical means to beat copy protection.

The ruling means you can't be sued for jailbreaking. It doesn't give you a constitutional right to an unlocked phone, and it doesn't oblige Apple or AT&T or Google or HTC or whomever to support a jailbroken device. It certainly doesn't impair their ability to use technical measures (aka, fixing bugs) to impair your ability to jailbreak.

Since no one had ever been sued for jailbreaking (and similar policy was not applied to, for instance, the PS3), the practical effect of the copyright ruling was close to nil.