Humphrey was caught in discussions with Melbourne coach Steven King in last year's trade period, but the club held firm in keeping him.
The Victorian-born 21-year-old was understood to be on the radar of several Melbourne-based clubs this season.
"The last five weeks ... I have put it all aside and (now) come to my decision," he said on Monday.
"I can go into the off-season with a clear head and just focus on footy and the footy club.
"They (the Suns) gave me the opportunity to live out a childhood dream, and I'm probably not the easiest bloke to deal with, so just to give back to them and I want to see success."
The 82-gamer had been contracted until the end of next season, but a fresh two-year deal ties him to Gold Coast until the end of 2030.
Meanwhile, Melbourne midfielder Tom Sparrow has rejected overtures from Port Adelaide to remain with the Demons.
South Australian Sparrow, in the midst of a breakout season, had been heavily linked with the Power.
But the 26-year-old has inked a five-year extension with the Dees, where he has played 139 AFL games.
"Tom has grown into one of the competition's most impactful midfielders, while also establishing himself as a valued leader within the club," the Demons' list manager Tim Lamb said.
And Adelaide defender James Borlase is believed to have snubbed offers from rival clubs to sign a three-year deal with the Crows.
The 24-year-old played just 16 AFL games since being signed in 2020 until 2025.
But this year he has established himself as a regular, playing another 16 matches.
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