Never going to happen. Will not hold up in the courts.
NPV will fail as soon as it’s tried. If enough states did sign NPV, and say a Democrat candidate with the popular vote won because of it, the electors would overturn the election immediately.
States who denied a candidate their electoral votes because said candidate lost the popular vote, would still have voted for electors from the same party as whoever won that state. Doubtful those electors would vote for a someone who stole votes that their party rightly won.