I would be interested to know where the thinking is going... Important for us to start planning how we will use them. Currently we are using hub sites for departmental intranets/workspaces. That works great as we have one hub site that manages the look and feel across several comms sites, community sites and team sites. Same MO for all departments and we are fairly pleased with it.
In terms of the Home sites, this would make sense as the root site collection of each tenant. But it is critical that it sits above Hub sites and Comms sites. So a heirarchy if you will. This is important to ensure that the organizational content and mega menu of the home site is always up top, then the hub menu and then the comm site menus as you change context. That's a lot of menus, but I leave the mechanics to clever people at MS. But for me home sites should definitely cater to this reality that I think many of us have created by now. It would be terrible to lose the home site menu when you go to a hub site. Already navigating the various apps on O365 is painful. For a real digital workplace experience, it would be good to make SP the hub of everything and allow a menu item that goes to those apps and the apps load under the home site or hub menu. I hate it, and users do too, when you lose context suddenly. But I can imagine it is not as straightforward as it would seem!