When we've stopped development on a game in the past, (recent examples, Planetfall, Battletech, CK2), we've been quite clear about it in our communications.
I hope you don't stop growing Imperator. It's really in a place that's good and now it needs content as the game play is really enjoyable.
With that said, a humble suggestion:
Put 2-3 people on Imperator to fix bugs only -- it's a small team and they don't have to be full time on IR.
1. Create this team before the Steam Summer Sale.
2. Announce that a team for Imperator has been put together about 2 weeks prior to the Steam Summer Sale.
3. Have one of them post here that they are beginning work on fixing bugs.
This will generate positive buzz before the steam sale, it will ensure it's not a "dead/abandoned game" which will give a positive perception to would be new buyers and will be encouraging for people to pick up the game on sale while it's in a good playable state.