https://www.meathchronicle.ie/2023/01/18/is-the-navan-rail-line-dream-back-on-track-cabinet-expected-to-sign-off-on-2031-start-date-for-e750m-project/
It is happening, but only signed off for now, it probably wont entirely follow the original trackbed closed in the 60's and lifted in 1964 either, as it needs to go closer to/into Dunshaughlin and bypass Kilmessan Junction, so the famous Station House Hotel can stay. A lot of the original trackbed from the MGWR route remains and most of the buildings too - Batterstown, Bective, Drumree and Kilmessan Junction
Plenty of bridges will need to be build also, at least 1 if not 2 crossings of the M3 along with some major civil engineering work elsewhere on the route