For all his talk of retiring to watch the sunset, this is a man who craves power.
Rather than creating unlimited food or making the planets bigger or something, he chose to use his abilities to kill on a massive scale; that’s not a guy who gives up power easily.
There’s no guarantee that this is actually what happened to the Gauntlet, but if it was, then you can bet that it will still be the centerpiece of the Avengers 4.
The heroes need some way to undo all the death caused by the Mad Titan, and I find it highly unlikely that Thanos himself will just leave the Gauntlet de-powered.