This move makes sense. Gwynn should be playing every day rather than sitting on the bench. I would expect the Brewers plan to play him every day somewhere next year, post-Jenkins. And I'm sure whenever they decide to cut bait on Kevin Mench's useless tenure as a Brewer (if they can find a sucker to take him), Gwynn will be back up.
Gross may not be hitting very well right now, but he's a pretty decent player and still young. He's not someone you just cut ... see previous administrations' debacles with cutting Troy O'Leary, Ronnie Belliard, Mark Loretta, Bill Spiers, et al, all of whom went on to shortly have better seasons than who the Brewers replaced them with.