Pointless winding up the Beamish brand, especially since last time I checked they seemed to be trying to market Murphy's as the "upmarket" stout. If they keep Beamish they'll have a stout competing on price too. In which case they'll be trying to chip away market share from Guinness from two angles.
Anyway, there's no guarantee that Beamish drinkers won't switch to Guinness if they wind up Beamish.
They'll also be ensuring that no one else tries to encroach on the market by ensuring they're competing against 3 other brands and not just two.
For those reasons I can't see Beamish going, wouldn't bet against the production moving though.