In my experience, when a gold edition is released of a game, that marks the end of its development. Altough i am author of a few expansions, doesn't automatically mean that i know more than any of you. I am not a part of the developper team and i never was, i am merely a modder who had the fortunate luck to create of few expansions who were approved by Slitherine and Alex (the lead dev); otherwise they would have just ended up in the mod section.
I was asked to create another expansion for Panzer Corps, and i began working (with the little amount of spare time i had available) on a USSR Grand Campaign but the timeframe i was offered (with Gold edition release already planned), it was far too little time to create a series of DLCs for the Red Army. The eleven scenarios of the first DLC of the USSR Grand Campaign, have been released as an non-official expansion of Soviet Corps; you can find it in the DLC upgrade project.
Panzer Corps is already over five years old, and apparently for the gaming business nowadays, this is a very old game. We surely don't have to agree, Panzer Corps has still a lot of potential, but these are the facts.
Some time ago, i started a thread
http://www.slitherine.com/forum/viewtopic.php?f=121&t=73188 about Panzer Corps 2. If you'd like, you can add your 2 cents there. Due to the success of Panzer Corps and still one of the most revenue generating games of Slitherine (this is public knowledge), it would be (commercially) impossible not to create a successor . This is all that i know.