My question is the title: Will frozen chat rooms be deleted? I am interested in particular in the case where nobody talks in the room for years.
In the chat faq there is an item on retention, which says the following.
Rooms will exist indefinitely, so long as there is at least one person actively talking in the room. A room is considered worth retaining if it has more than 15 messages by at least 2 users.
Rooms not worth retaining which are inactive for 7 days will be deleted. Rooms worth retaining which are inactive for 14 days will be frozen. Frozen rooms do not allow any new messages to be sent, and are not shown in the default room list to prevent cluttering the rooms interface.
This is slightly ambiguous to me. The text hints strongly at indefinite retention of rooms "worth retaining". However, the only real guarantee that appears to be made is "Rooms will exist indefinitely, so long as there is at least one person actively talking in the room".