Every time I see the word secession, I get excited thinking someone is getting things together for the good of the nation. Only to be brought back to reality..... I do not see it ever happening these days. Probably a good thing.
The key point to remember is that all such changes require mutual consent, but mutual consent is the one commodity in very short supply these days.
Amendments to the Constitution, a convention to rewrite it entirely, secessions and new Confederacies are all within the scope of the Constitution providing, providing, providing everyone agrees to them.
But of course, if we had all that much mutual consent, why would anyone want to change everything?