The Cask Report has just been published. In general, it is good news for cask beer with sales up in 2011 by 1.5% and static so far this year. Measured against an overall decline in the beer market that's reason for optimism.
However, micro-breweries are still opening and existing ones expanding at a fair rate so which cask brewers are in decline? There can't be much more market share to take from the decline of the former 'national' brands like Boddington's and Draught Bass. The bigger players such as Marston's and Fullers have reported increased sales and Coors' purchase of Sharp's has seen Doom Bar production rocket.
I'll wager that the remaining family and regional brewers are the ones struggling to keep their heads above water. Unable to compete with the likes of Wetherspoon's on price and with brands seen as old fashioned and irrelevant to the committed cask or craft drinkers I predict more takeovers in this sector soon.