I think it would be incredibly short sighted to sit on 40m in expiring deals and not make a move. They have plenty of future picks to use, and they can't keep everyone, not do they have the minutes. The core of this team is pretty well solidified, but it's not perfect. There is room to improve, and they could add a good 3pt shooter without losing anyone in the current rotation. Reed needs time to develop, he's not going to be the sharpshooter they need this year.
This team positioned itself with lots of trade chips, and I think they should use some instead of letting them expire this off-season. This is our last year of cheap Sengun and Green, so if there is a way to get a good player for essentially junk contracts and future picks, they should try and make a move.
Maxey isn't going anywhere, he's a foundation piece that you build around.
I think some realistic options would be gettable are Walker Kessler, DeRozan, Chris Boucher, Cam Johnson, Olynyk, Valanciunas and Jordan Clarkson. All those guys are on teams going no where and looking for picks and expiring contracts. Getting a C that can help with time protection would probably help with some of the bigger teams in the playoffs, and another scorer off the bench would be good to have. It also helps insulate the team against injuries and adding depth.