No they won’t. They’ve had a referendum and they don’t have a mandate, or the legal right to call for another one for many years to come. It wouldn’t make sense for Scotland to leave the UK to rejoin the EU. Over 70% of Scotland’s ‘external’ trade is with the rUK and less than 18% of it is with the EU, it would make no sense whatsoever to leave the UK over the EU. As for NI, well, that’s up to them. The idea that there would be border controls is scaremongering nonsense though. The CTA and free trade with Ireland long predates the EU and it is not in Ireland’s or the UK’s interests to see this stopped, and we are also Ireland’s most important trading partner. If pushed too far, Ireland would be the next to leave the EU.
About whether it makes sense for Scotland to leave the UK, you are correct -- economically it does not make sense, but the same argument could be made about the UK leaving the EU (since 44% odd of the UK's trade is with the EU). Economics play a role in people's minds when deciding on a referendum, but emotions seem to play a larger role
As for Northern Ireland -- your point is also valid, it could go the other way with Ireland leaving the EU.
The reason I don't understand it is that they have lost their native language and much of their culture seemed to me reduced to "William Wallace" and "we aren't English"
But they have this nationalism, and it is emotive. Now its based more on "dang Tories"