Once enough states join the National Popular Vote compact to clear 270 electors, the electoral college will be nullified in practice. It may take a couple more decades, but it'll happen eventually.
Don't worry. The first time a Republican wins the popular vote, but Democrat carries the state, people will cry about their vote not being counted in THAT race, will drop out of the compact fast, and electors will probably defect no matter what the state does. NPV doesn't really solve the problem.