While no one really knows what will happen to the British pound after Scottish devolution (if it happens), it is apparent that in the short-term it would have a negative impact on the pound. Theoretically, Scottish independence would cause uncertainty, and currency markets do not like uncertainty at all. Investors would start selling their pounds, which would cause downward pressure on the valuation.
With scottish independence GB pound hit the bottom low in no time. There is bound to be long and short time negative impact on the GB pound. With the debt sharing issues and other critical issues the GB pound has fallen sharply in exchange rates in recent days and will continue to do so due to interdependence of world economy.
No, don't think it will have much of an effect on the pound at all. I don't think Scotland having independence will negatively effect the currency all that much. I feel that the pound will be just fine with or without the country. I think there will very little change if any.
An independent Scotland would not have a long-term negative impact on the GB pound. This is because the size of the U.K. has been declining for years with no palpable dissolution of value in their currency outside of normal fluctuation. The GBP will be normalized within a few days if any reaction did occur.