Both parties are dying, its just that they still have a strong strangled hold on the government. That is why you see independent and other party members join one of the two to get votes for a major election they want the office to. Parker and currently Sanders who was an independent but became a democratic to get the votes. Davis and Williams who was an American Independent Party member but became a republican to get the votes. There are other parties out there that win local, county, district, or even a State election here and there, but when it comes to the National Election, it is hard for them to win. That might not be the case for the other parties in the next decade or two.
Everyone is waiting for both parties to fall so they can rebuild them, but the fact is that these parties have fallen before and flipped on there past issues. The Deep South is a testament to this, as in the views switched parties.
Best President who was a Republican was Eisenhower, but he would be too liberal for that party today.
Best President who was a Democrat was FDR, but he would be too conservative for that party today.
It is a funny thing. Both parties live in their own bubbles. Just keep an open mind when listening to the media cause Fox and NBC are two of the biased network's out there in the United States.