I think you can throw the projections out the window. Everyone likes to speculate as to what he really is but no one can be too sure.
The "safe bet" is something like Drungo outlined above, but let's be honest...that's boring. And there's nothing to romanticize there.
The exciting prediction is that what we're seeing right now is legit and he's something like Tony Gwynn/Rod Carew/Ichiro. That's not likely.
The truth lays somewhere in the middle, most likely. To which side it leans is to be determined. But @Tony-OH is correct; he was a much better hitter from the left side to begin with and nobody can remember someone giving up switch hitting at the ML level, much less having the success that Mullins is having. We're somewhat in unchartered territory here.
Either way, I'm having a blast watching him.