It's actually kind of insane that USUM couldn't even sell half as many units as SM did. I know it was basically the same game with a few new Pokemon, but not even half? Man I wonder how well PLG is going to do. Hopefully it tanks so they know this is not the right direction.
Consider that, aside from what Wallace said (third versions/remakes always sold less, often significantly less, than the main game), the trend doesn't really impact PLGO.I don't think it necessarily the wrong direction, it appears to be a pattern that primary versions sell more than remakes and 3rd versions. Here:
No matter how much they keep calling it core game, the fanbase has accepted it as basically a Coliseum-level spinoff, so PLGO sales should not really give any "signal" about the direction of the development. The only signal a PLGO flop could give would be that they completely screwed up with the marketing trying to sell a game to a playerbase that doesn't want it, but that's about it.
Plus, people discredit USUM way more than they should. USUM was a good game, SM is the error that should never have existed :P