The old argument was offense was up because there weren't enough good pitchers due to expansion. But we can actually locate what's causing the run environment to depress, its not some mystical thing that we can apply to whatever we like. The strike zone has expanded (down) and there are more pitchers that can throw harder. The latter might be affected by expansion a little bit, but the former will be completely unaffected by expansion and the availability of talent. So at the end of the day there'll just be more teams requiring more position players that can't handle the expanded zone.