I believe the hotel is set to open in 2021/22 from what I've seen. They are getting a junior/family coaster next year, presumably 2 more flats as well. Their biggest investment is set to be in 2019, with a major coaster, which I'm 99% sure will be a Mack or B&M, and there were whispers of the dark ride opening then, and if not then, I expect one in 2020. I'm pretty sure they'll be a coaster in each of the next two years though, can't say for certain what they will be/what else will come, but we've got 3 new attractions by the looks of things on the map this year.
I must say though, it was apparently a bank holiday in Ireland, and the park was quite quiet on Saturday, quite a few walking round, but everything was walk on, when I was on power surge there was literally no one else in the queue, and Cu Chulainn had half full trains at points. Maybe people are waiting for the Viking Voyage, which looks very well themed!