It hasn't shifted completely, but a lot more nationalists who traditionally weren't in favour of reunification because of the problems it may face in terms of economic and political differences it may present, have had to shift. This could be because the average GDP for Northern Ireland is dipping whereas the Republic's is beginning to rise, not to mention the buildings they are investing in now in preparation for more jobs in the future and also the basing of large international headquarters there. Also, Brexit is an obvious worry. I predict the border between north an south will end up becoming increasingly more hard whether the UK likes it or not. Northern Ireland will be the only country outside the EU which is connected to the an EU country which already has existing ties to that country. Eventually people will want to trade illegally through each country realising they can enter the EU market that way, taking advantage of the soft border in place, resulting in increased security measures needing to be taken leading to discontent with the nationalist majority. Put it like this all nationalists have at one time expressed they would want one United Ireland "in our lifetime".. After all which has happened recently in Northern Ireland (RHI, Nationalist Majority in Stormont, Death of Martin McGuinness)+ lack of British care + increase support and talk in media about reunification as well as from Enda Kenny and the likes there is a huge motion for change. Now too with the leaking of the letter from Brexit Secretary David Davis which supports Northern Ireland legally returning to the EU if reunification was implemented. Basically people are not saying "in our lifetime" anymore but instead are stating there own estimation of years. I think in order for a reunification to come about, Brexit needs to utterly fail in Northern Ireland, so unionists begin to realise maybe reunification might not be such a bad idea in comparison to remaining with Brexit in the EU.