Thanks everyone for the great feedback. As CabbageDad said, "I would venture to bet that he also pulled more balls than usual. Not at all uncommon but not a reason to switch. As he grows in size and strength, he will develop power from the right side while maintaining all the other benefits. " I had the growth of size and strength in the back of my mind, and I know the power will come - we just need to keep working on developing the swing.
He did pull quite a few in the bucket of soft toss, but he hit a lot right back up the box.
My initial thought was to get him to switch to lefty and only lefty, but given that he is 12 and has a solid swing righty, I think that might be foolish. As MuskyShane said, "My biggest advice is switch hitting is 2X as much work - if everyone else is hitting 3 times a week with their regular swing, your player needs to hit 6 times." My kid will work - that I have no doubt. It is time that is our issue. With schoolwork as priority one and then hockey being the in-season sport starting September 1, our time to hit is limited. If we are going to put in quality work, it's got to be on hitting right-handed.
I am still going to have him put some tee work and soft toss in hitting LH, but not really push the issue. Now if he really wants to pursue this, that is a different issue we need to tackle...