The recent signing of Frazer Richardson means that the Tractor Boys have cover for the right-back slot and McCarthy is content with Hewitt earning first-team experience on the South-East coast.
On Hewitt's time with the Gills, McCarthy told Ipswich's official website: "We will see his true mettle. We will see then if he can come back here and start next season in the first team. It's the same with Frederic Veseli (on loan at Bury).
"I had a chat with [Gillingham boss] Peter Taylor and told him I'm looking for an experienced right-back and if I could get one in, I'd discuss Elliott staying there.
"He's doing well there, Gillingham want to keep him and I'd be happy for him to stay there."
Wales Under-21 international Hewitt has made five starts for the Gills in two separate loan spells this season.