The game gets a lot of negative feedback and many players i know have stopped playing the game. That is not, like a lot a people speculate, because of the current balance issues or too few races but simply due to the baffling lack of single-player content and thus lack of replayability.
The campaign itself can only keep you entertained for so long. It's a linear campaign without too many choices or optional missions involved, additionally quite a few people disliked the overall style and story of the campaign (make of that what you will i don't really want to get into wheter the campaign itself really sucks or is quite good).
But i think it's safe to say that there isn't much incentive to play the campaign more than once.
So if we wil see another big content release it might be beneficial to include some way to entertain the single player crowd for longer than one campaign playthrough. A good foundation for a solution has already been given by previous iterations of the franchise, in this case namely Dawn of War: Dark Crusade and Soulstorm -> the Metamap style campaign.
As i mentioned, this sort of campaign only offers a good foundation for an enjoyable single-player (and possibly multiplayer as well) experience. The Dark Crusade and Soulstorm campaigns got their fair share of criticism too, and deservedly so.
Besides the elaborate stronghold maps the campaigns offert a lot of skirmishes in between (which could feel like a chore) and very little story. Nonetheless the act of conquering a whole planet/system/sub-sector/whatever with your favorite faction gaining global bonuses on the metamap and purchasing new wargear for your commander was pretty fun.
So why do i think this could be used for a fun gamemode in Dawn of War 3 and how do i propose to do this.?
Well Part of this has already been discussed in another thread quite some time ago (i think "will there be a dark crusade stile campaign" ... or something like this if you want to check it out). As i said, the basic principal of such a campaign can be very entertaining and with a few tweaks and improvements could lead to a fun experience for single- and multiplayer as well as creating a nice platform to bring out new content and possibly offering nice statistical feedback for relic.
The basic idea would be to create a metamap similar to those in DC or SS. There are several areas to conquer, could be
1 planet = 1 area or 1 planet = several areas or both and some of the areas could award small global bonuses for the faction holding the area just like in DC/SS. One conquest could run over the course of a certain period of time or until the whole map got conquered until it resets (i'll refer to one such "playthrough" as crusade from here on).