It would still require a 2/3 majority, but, hmm, I can't think of a good example, but as people get more used to something it tends to become easier to do, even if it requires a large proportion of people. For example, suppose one politician cuts a deal with another to gain their vote on an amendment that will really help them, in exchange for voting for an amendment the second guy proposes, that the first guy would either abstain from or vote against.
And also while the SC can "interpret" laws, it can't blatantly contradict them. It also has to decide when to back down, as it is totally dependant on the other two branches for enforcing/abiding by its judgements. If Congress passed a law in contradiction to the Constitution, and the Executive branch supported it, and it had popular support, there's not much the SC could do beyond punish individual violators. Especially since I don't think judicial review is legislated at the constitutional-level.
I don't see it happening with the current political situation, but still, the SC is not all-powerful.