has found a listing for Valve on the official GamesCom website
, listing them as an "Exhibitor", and then adding "Strategy" to the description of what they're showing.
Obviously the only game in the Valve stable that even remotely fits the "Strategy" genre is the little-talked-about DOTA 2. Moreover, when I visited Valve earlier in the year, they revealed to us their next showing wouldn't be E3, but more likely GamesCom, adding weight to the idea they'll be showing off the game in proper form since it was initially announced.
AusGamers is currently exploring our own GamesCom journey, so stay tuned for more as we have it.