There is now. Leaving the EU actually brings the Ireland debate away from typically nationalist/unionist politics to actual real issues. If the Republic has to secure it's border with the North (as I believe countries on the border of Europe are required to do so) consider the impact on people who live in border towns. A lot of people living just within the north side of the border work in the south and vice versa - they would have to go through border control every morning and evening. And what happens to the large number of ROI citizens living and working in NI (and vice versa). This actually opens the debate on unity up and brings it past the typical dividing line politics. It will also likely fuel nationalist support as the democratic will of people in NI (and Scotland) is essentially ignored thanks to people in England. It's a very strange situation. I think it's still highly unlikely but if Irish unification is ever going to happen this will be the catalyst.
It's just not that there would be border control, there's also question would they need visas to get through the border control?
No need to be condescending. Border controls are one issue. I didn't say they were the only one. Today's decision is going to cause many issues for Northern Ireland and if a persons daily life starts to get affected by the decision they might eventually be willing to put to the side their built-in unionist/nationalist mentality and figure out what's actually best for the people. I don't know what that is but ruling out unification or independence would be silly.
http://www.independent.co.uk/news/uk/politics/brexit-norther...
The EU train is leaving and governments need to make a decision whether they want to get on or stay off.
Scotland is less messy and would separate fairly easily imo (but you never know British nationalism is on the rise so letting them leave could be seen as something to prevent at all costs)
This would be the first time that those who want Irish unity could actually sway a significant number of unionist voters. Violence would ruin that opportunity so I doubt it would happen. This vote has increased the possibility of their goals being achieved politically. If anything I would expect violence to rise on the unionist side if it did look like a border poll was going to take place and not go their way.
Northern Ireland has absolutely no chance of seceding, they can't go it alone as a separate country, and there's absolutely no appetite for unification from either side.