Navan Line was discussed to death 10 and more years ago here. There is a spur which can be used into Connolly, but to be realistic you are waiting for the DART expansion and perhaps a railcar shuttle to/from that expansion.
Navan via Dunboyne is not a runner if it ever was then the Motorway has canned it. The idea of development now is for it to be much closer to the city than regional towns such as Navan. If you believe that there will ever be any planned development.
We are the passengers