There is no future for Republicans. Trump is the only thing holding them together as anything resembling a coalition. Eight years of looking for someone able to match his energy has failed. Trump's inevitable death will be a murder-suicide pact for the GOP.
There is no future for Democrats. They lack the ability to inspire the people. Their options are to cling to a framework that has already failed, or try to be more Trump-like and authoritarian against their "enemies", which they lack the competence, drive, and/or chutzpah to make work.
The bright future for America is a cross-party coalition that rejects R and D tribalism and forges something new that a majority can agree on. But both sides are so divided, so petulant, and so untrusting of one another, that its unrealistic to expect such a positive change in the near future without an even stronger catalyst.
The dark future for America is complete anarchy once people openly accept that no system exists that really controls them in any way.
The median is maybe we dissolve into 50 independent countries if people pretend they're still willing to accept State law after the federal government falls apart, but the cognitive dissonance to believe that is already structurally unsound.
What is government when people refuse to be governed?