By 2030?
I think it's certainly a possibility once Brexit settles in for the long haul.
The EU have said they would basically absorb a lot of the cost as it'd be a reunification situation. But realistically it would be a devolved province, with some self governance in Stormont. It wouldnt look all that different day to day, it's just the maps would look different. Simon Coveney has said it wouldnt and couldn't be ruled by Dublin as it would be too much of a pill to swallow.
There's absolutely no appetite for it in Dublin, because it's a logistical nightmare and a money pit. What government wants to oversee that? So they'll kick it down the road as long as possible.
But if Brexit really starts to make things messy in NI then there might be an appetite up there, even amongst Unionists, for exploring what it might look like to rejoin the EU under ROIs umbrella.