Interestingly, this might lead to home rule in Scotland as well, and with it a push towards federalism in the UK. That might spur a movement towards federalising the Empire, which would allow it to remain one of, if not the, most powerful states into the 21st Century. Part of the reason for the 1916 risings was that most loyalist Irishmen had enlisted in the British Army and were off dying in the trenches. Without the war, I'd still expect a fair bit of terrorism and some unrest in Northern Ireland, but not as bad as OTL.