Yep, I predict violence and turmoil. The peace process had more or less laid the demons there to rest. Northern Ireland will not want to join the bankrupt republic the state it is in, but a vocal minority of republicans may want to start trouble again. This really was a sleeping dog that should have been left to lie.
De-stabilizing, at a minimum. Republican sentiment in Ulster certainly relates to ardent Scottish nationalism and will be electrified by what they perceive to be the ease with which Caledonia was perhaps able to democratically remove itself from the Union.
Act II will be in the Six Counties.