I'm not so sure it will not go ahead in some form or other. Ceannt station is unique amongst Irish provincial city centre rail termini, insofar, as it is a truly city centre. It is only 250m (approx.) from train door to Eyre Square.
Given the extent of the proposed site, it's location and the ever insatiable demand for commercial and residential property in Galway, this is a particularly valuable and easily disposable piece of real estate for CIE. They would make a tidy profit and end up with a brand spanking new Rail/Bus terminal.
They have, of course, yet to get planning permission. The application will be lodged in September we are told by CIE. It is likely there will be a raft of objections from local interests and already we have heard Micheal D Higgins TD (Lab), shout down CIE's apparent lack of consultation with the local community. He has also expressed concerns about the nature of the development questioning the ratio of commercial use to transport use, fearing the transport element of the project is taking second place to the profit making commercial/residential parts.
This project is likely to go ahead, perhaps not as we see it presented in the plans to date, but it will happen and probably within the stated timeframe too.