Will the Democratic Party collapse if they don't embrace Bernieism?

[°Leprechaun]

The Democratic party has been going downhill since 1964. Obviously it is also deeply divided. It was divided as far back as 1968. Obama did ok in 2008 and 2012, but he didn't have good coattails the way candidates did in the past. The party is dieing in many places, especially the South.
Obviously, no candidate since 1996 has done well in the South in POTUS elections.
A lot depends on what happens in the next three years, especially if Democrats can start turning things around, (11/2018, for example). It is hard to predict what Trump will do. The stock market seems to be ok so far, but there are other factors, not all strictly economic.

If Democrats could reach beyond the extremely narrow groups that they are pandering to they might do better.
Republicans can pander to the tea party and the so called "religious" (aka so called "christian") right and get away with it because those groups are bigger than the groups to which Democrats are pandering. Perhaps they need a better economic message. Sanders seems to have done better among certain middle class voters in two key swing states, MI & WI where he won the primaries.
Democrats have done an excellent job of alienating Bernie voters taking their votes for granted and some would even blame him for Clinton's loss and not put any blame on Clinton herself. Can and/have the Democrats considered if any potential candidate can or could bring the disparate two factions together or will they continue to eat their own?