I would bet on England and Wales voting to leave, and Scotland and NI voting to remain, with the net result being a narrow Brexit win, triggering calls for a new Scottish indie referendum.
I'm curious as to why the implications for Scotland have been widely considered whereas Northern Ireland has been almost entirely neglected, even though it is the country with the most to lose, both for political and geographical reasons.
Brexit has implications for the peace agreement - unless free movement is retailed, then a physical border will need to be reestablished and this has enormous political significance. And it would leave NI curiously isolated - separated by a wall from the country with which it shares both a physical space (the island that is Ireland) and parts of its cultural heritage - and by the Irish sea from the rest of the state to which it is politically bound.
Economically, Ireland is also much more dependent on the EU than other parts of the UK because of the integration of the southern and northern Irish economies and because of its reliance on European agricultural subsidies.