The League of Ireland First Division champions are set to receive a £90,000 transfer fee for the 19-year-old, who impressed while on trial at Playford Road.
McCarthy told reporters: "I think he will, eventually, be a first-team player. Whenever that is, I don't know."
This is not the first time the Tractor Boys boss has recruited from Waterford, with Daryl Murphy signing for Sunderland in 2005 when McCarthy was in tenure.
Furthermore, winger Jack Doherty signed from the club to Town in 2013 but was unable to break into the first team and returned to Ireland.
Ipswich also had Waterford's John Martin on trial, but McCarthy said: "At this moment in time there's nothing happening on that one."
The Tractor Boys currently sit eighth in the Championship, two points from a playoff spot.