Right at this moment, development is going splendidly - no doubt because I am still on holidays, and recently back from a very relaxing (no code) - and inspirational - trip to Venezia and Verona. That may change once I'm back at work next week.
Finishing date: I think I've mentioned a couple of times, I don't do those. Imperium is my hobby, sorry. I will bend a little on my principles, though, and say that I hope to finish Imperium at the latest before the end of next year. Not sure if that helps though.

Advertising, testing, etc., will all wait until there is a near-finished product to advertise and test upon. Don't worry - you'll read about it here first.
I don't want to rewrite any more feature lists, so I'll wait a bit with that. As for modding, almost everything (including major parts of the game interface) is stored in text files, so the game should end up very mod-friendly.