I have to imagine that CBS is already of the mind that they will continue to produce Picard for as long as Sir Patrick Stewart is willing to play the role.
As for Picardo, if they bring him in as Zimmerman that will make the third show that the Zimmerman character appeared on. REmember that the first time we saw the flesh-and-blood Lewis Zimmerman was actually on Deep Space 9 rather than Voyager.
Maybe after Stewart leaves, they'll continue the show as "Star Trek: Picardo"....
Or, perhaps he's playing Picard's brother, back from the dead. Who wouldn't want to see this in the credits:
Patrick Stewart as Jean-Luc Picard
Robert Picardo as Robert Picard
