There have been times in the past when the Democrats looked dead and they came back. Same with Republicans.
Right now Republicans have a lock on white men. The single largest voting block in the country. It's at least 60/40. White women are about split.
The black vote is monolithic. But it remains to be seen if they'll come out and vote if they don't have the option of putting a dark guy in the white house. Besides, most blacks live in red states. They are the least important voting block.
Asian americans are overwhelmingly Republican.
The future is Latinos votes. Right now Democrats are ahead with them. But republicans have been able to do ok with them in the past and should be again, if they can overcome the tinge of racism in a small corner of their base.