This article in Vox says that if the predicted blue wave is big enough and deep enough in legislative and Governor elections in certain states, the National Popular Vote plan may go into effect before the 2028 presidential election.
With the recent passage of the compact agreement in Virginia, states that have 222 electoral votes have passed the compact. Only states with at least 48 more electoral votes need to pass it for it to become effective, pending, of course, the inevitable legal challenges.
The article says that the targeted states for the compact’s advocates are Wisconsin, Michigan, Arizona, Pennsylvania, Nevada and New Hampshire.