Honestly in my opinion, the devs need to give incentive to play other factions while single faction campaigns are happening. Otherwise we get what is currently happening, long queue times and no one wanting to play any other faction then what is currently up for campaign.
A little late now as adding incentives for the other factions might tip the balance in player #'s, and a faction might not win during their "faction week." I just hope, once the Eldar and SM weeks are done, they don't this style of campaign again.