United secured their 20th league title on Monday night to end their fierce rivals' hopes of lifting the trophy for a second successive year.
Gill, who will step down from his position in the summer to push for a place on UEFA's executive committee, expects City to respond next term.
"I'm sure they will come back," he said. "They've got some ambitious plans on their investment and their academy. But that's what the excitement of the Premier League is.
"I'm sure all the clubs who missed out this season will be doing business in the summer - as we will be - with a view to come back all guns blazing next year."
Gill also credited United's owners the Glazers, who have overseen five title wins and Champions League success since completing a takeover in May 2005.
A minority of United's fans continue to criticise the Florida-based owners but Gill said: "They have shown that what happens on the pitch is crucial to the club's ambitions off it.
"There are still a small number of dissenters and they will always be there and they have had long held views which they are not going to change. We respect those, but ultimately, someone has to own the club.
"They [Glazers] get the personal enjoyment and the important thing is that there is really no ego about them. They operate behind the scenes here, they don't walk around saying 'we own the club', and they are very mindful of the traditions and the history of the club and people.
"Clearly, if you own an asset and it comes up with winning a 20th title, it's unbelievable."