Brexit will be the route cause of breaking up the UK alongside the oft quoted 'non-reforming' accusation aimed at the EU. The UK should have got its own house in order first with a long over due reform of the Union. It is patently obvious that Scotland will in time become independent of the UK as it exists. Whether it is next year or in 5 years. People may say the polls show there is no appetite for it but the ballot box tells a different story. The SNP have been re-elected to Holyrood, not long before sending a record number of MPs to Westminster. Everyone knows what the SNP stands for ultimately and they are continually elected it is disingenuous to suggest they have no mandate for their overarching, principle, existence. Further, the fact they are far more competent in power than Scottish Labour or the Tories is a massive benefit. With council elections looming it will be welcome to see the last of Labour kicked to the kerb!
Simply, Brexit is the bomb that destroyed the United Kingdom as we know it. I have no doubt that if offered, a new agreement, after realisation of the component parts of the UK as sovereign nations, implementing similar administrative model as the EU to which all four nations are equal partners. How difficult would it be to accept and acknowledge all distinct parts of the UK as separate sovereign states and go the EU route with it. Own governments and perhaps regional in England if called for subservient to national governments under a UK council for reserved UK issues (defence etc.). It would be taken in a heartbeat by the people in Scotland and elsewhere within the UK. It would likely go some way to addressing the populist movements we have been increasingly seeing.