The issue here was a Federal judge re-writing citizenship laws to create a constitutional citizenship entitlement. This SCOTUS has thrown out lots of crap that got created with Justice O Conner's assistance and that would be another one.
How about the SCOTUS (yes, the supposedly "conservative" SCOTUS in 2007) ruling that CO2 is a "pollutant" despite the fact that congress did not intend the Clean Air Act to regulate CO2?
How about Plyler vs. Doe 1981 (Texas has to pay for school for illegals), another misinterpretation of the 14th amendment, despite the fact that the authors of the 14th said it does not apply to illegals?
I never can predict what the SCOTUS is going to do. It often defies reason, especially with bleeding heart issues.
A couple of other unfortunate factors:
It takes so long for an appeal to get to the SCOTUS that the number of illegals (or whatever non-citizen category congress defines) would increase dramatically by the time the SCOTUS rules. Then they could argue that they are in legal limbo, and that deportation or being expelled from a "path to citizenship" would be out of the question.
Imagine Obama is reelected and one of the relatively conservative justices has to be replaced....
But as you said, at least for the time being, no amnesty can pass congress.