It's a roster construction you don't see very often anymore (and no the emergency catcher -- Pedro cough Feliz -- doesn't count) but it just might be the Giants will end up structured this way next season.
First you have to assume a few things: Molina won't be traded (he'll be the front line catcher next year) and there won't be any big moves by the Giants to sign a free agent 1b or 3b.
The latter being true, youd' have to expect Sandoval to see a lot of time at those positions when he's not giving Molina a day off behind the plate (i.e. caddying for Zito).
But on days when Sandoval starts at a corner, you simply can't pinch run for either before the 9th inning without a third catcher on the roster. It's not prudent; you don't want your last real catcher coming out with an injury in the 7th inning of a close game because the other team will steal more often than Ruben Rivera in an unattended locker room.
So, it could be that the Manifestation of Pablito is the best thing that ever happened to Steve Holm's bank balance.
Any statement by Giants brass that "Sandoval's future is behind the plate" is simply not true, at least not longer than the gap between Molina's departure and Posey's arrival as the mainstay behind the plate.