I don't know. It's hard to guess how long a contemporary poet will be celebrated.I do like Muldoon though. He has astonishing technical virtuosity and a an intelligence that successfully guides a poem from one twist to another. Some people think he is too 'smart-alec' clever and too impersonal. But I enjoy his stuff and have learned a lot from him. He is also an engaging reader of his own work.
While I do think Muldoon is certainly clever, I would recommend three little-known (in the states, anyway) Irish poets: Leanne O'Sullivan, Paula Meehan, and Jessie Lendennie. Lendennie has a neat website and is editor of Salmon Publishing (and she is another fine soul who loves her Border Collie).