Proclaiming independence in Scotland will determine what happens to northern Ireland and Wales.
Northern Ireland exists as a result of its affiliation to a United Kingdom. With Scotland's independence the link in the chain that binds Ulster to the United Kingdom is broken as then the kingdom is no longer united.
The way is open for Ulster to unite with the Irish republic, as remaining as a dependency of England is not an option and the ties which bind unionist Ulster citizens are closer to the protestant Scots than to the English.
Similarly the Welsh do not consider themselves English (though many have allegiance to Britain). When Britain ceases to be a united "nation" the Welsh will not choose to be an appendage of England and will proclaim their own independent status. The Act of Annexation of 1536 will need to be repealed.
Thus Scotland, Wales and England will become independent nations within Europe and Ulster will be subsumed with the Republic, finally creating a United Ireland.