Here's how it works (subject to any refinements before we roll it out):
Guilds will have two additional options:

And when you go to a hub page you will see a couple of new things. On the left side of the Version box, there is a list of guilds this game is listed in:

On the right side is a new link for submitting the game to a guild:

Because it's a somewhat expensive hit on the database to calculate which guilds you can submit the game to, we wait until you click the link to figure that out, and give you a list like this:

After you've submitted to a guild:

The guild staff sees this:

If you have game management privileges for the guild, or if the guild auto-approves games, then it goes right onto the list.
The first draft of this functionality is in place and we should have it out shortly. We hope it will encourage guild membership and for games to be added to guilds.
We have several more ideas for how to add Member/Guild functionality to the hub pages, and of course we're interested in any ideas you might have.