Bruce Cain at The American Interest considers the future the party system,.
I am more inclined to think that U.S. politics is headed down a third path where we retain the duopoly form and the essential intermediating function of political parties, but the party as organization moves into the largely unregulated internet space. The history of U.S. political reform is that political activity gravitates into the areas of least legal resistance. This is no clearer example of that principle than campaign finance reform. We imposed stricter restrictions on campaign donations after Watergate, and it eventually gave rise to PACs, independent spending, and now Super PACs. We passed disclosure regulations, and big money found safer ground in nonprofit 501c4s. We tried to offset private campaign money with public subsidies, but the restrictions proved too burdensome, and presidential candidates now avoid the public finance system entirely.
In this third scenario, the Democratic and Republican parties are still dominant and favored in many ways by state and federal laws. But the political parties continue the present trend of morphing into networks of party affiliated groups that spend “independently” on behalf of candidates. Outside groups and social media figures with large followings enforce party discipline rather than Congressional leaders.