What are Jackson's major concerns for the future in his farewell address?
I think that one of Jackson's major concerns is the rise of sectionalism that he sees is a part of the American political dynamic at the time. Jackson recognizes that little good can result of the division between North and South. To this extent and to his credit, Jackson warned of a situation eerily similar to the Civil War, about 25 years ahead of it:
What have you to gain by division and dissension? Delude not yourselves with the belief that a breach once made may be afterwards repaired. If the Union is once severed, the line of separation will grow wider and wider, and the controversies which are now debated and settled in the halls of legislation will then be tried in fields of battle and determined by the sword.
Jackson speaks to this idea, that growing sectionalism and taken to its most logical extension cannot be a good thing for the nation. In an interesting pivot, the end of the addresses that laws and government action are not the only things needed to avoid such a predicament for America. Rather, Jackson suggests that individuals must rise up and believe that the preservation of the Union is vitally important. In this, one sees Jackson appealing and reaching back to the very idea that motivated most of his presidency, in that individuals must feel that the government is theirs and merge their own subjectivity within it. Jackson thus feels that sectionalism is something that arises from the people and, thus, can be controlled and limited by the powers of the people.