OK... I know that it's been a while. My attention has been elsewhere. This subject, however, is a good one for this sort of "long form" format...
So here's why "CalExit" isn't going to happen: The national Democrat Party will never allow it.
California is the beating heart and soul of the Democrat Party. Its powerbase is here. Democrat money comes from here. The Democrat-controlled media is based here. When they last controlled Congress, their majority came from here. There's a reason why Nancy Pelosi is still in charge of the House Democrats. Every four years, Democrat presidential candidates start election night with California's 55 electoral college votes in the bag; before a single vote has been cast here. When the votes were cast, Hillary Clinton won 2 votes here for every 1 Donald Trump won. The notion that Clinton won the popular vote exists only because of this disparity.
Next, let's look at the process itself. There is a procedure to admit a new state, but no mechanism for a State to leave the Union. Before California could secede, the Constitution would have to be amended to include a "divorce" clause. This is where the Confederacy went wrong. They thought that simply demanding to go their own way would be sufficient. Crazy Californians here are making the same mistake.
Now there are some in Red State America that might go along with a CalExit plan. These red States might be tempted to go ahead with plans to take 55 Electoral College votes, 2 Senators, and (at least) 38 Representatives away from the Democrats. However, there aren't enough red States to push through such an amendment. 3/4 of the States must ratify an amendment before it becomes part of the Constitution. Blue States would be needed and those Democrats would never let this happen. The last thing they want is to be members of a permanent minority party. CalExit would guarantee that fate.
Every last Democrat in California might want to leave the US, but every last Democrat in the rest of the country would oppose them.