The initial reaction would be extremely negative, but the threat by the Royal Bank of Scotland to break away from Scotland itself after a devolution vote would be a long-term boon to the stock. Scottish assets and account holders would have to beg and plead to keep RBS happy, while investors would be supportive of the move.
One thing that Scotland needs to be very, very certain about when the vote for independence comes up is that there will be a financial crisis at first. The Royal Bank of Scotland's stocks, and indeed most of the indigenous business in Scotland, will have a very rough time of it. The effects will not be positive for at least a decade after.
I feel that if Scotland does decide to break away from United Kingdom influence that it will cause a lot of uncertainty. I think that people will be afraid of the consequences and will be a negative on the market for quite a while. Any time there is a change people get nervous and causes them to overreact or be overly cautious.
Scotland`s break from the UK is considered as an economically destabilizing event and thus is expected to impact negatively Scottish business, including RBS. Currently Scottish business credit rating is matched to the UK`s state rating and a split will directly lead to downgrading, due to Scotland`s lower economic viability on a standalone basis. Lower state rating will negatively impact the stocks of RBS.