I may be skeptical on the whole thing (as usual), but wouldn't that be more in line with where Shovel Knight is more popular?
Shovel Knight is more marketable outside of Japan, after all.
I was going to compare him with Japan-only characters Roy and Lucas, but they're veterans... Japan likely doesn't know a lot about Shovel Knight... Though his inclusion in Smash could be a marketing stunt... Isn't the game going to release in Japan somewhat soon?
Another thing: we have no idea if the criteria for character selection has changed from DLC. DLC, as a whole, is an unprecedented situation, after all. We know what are Sakurai's methods for selecting characters... for the main games, that is. Main game sales have the people buy the whole roster, so he has some freedom in regards to putting unpopular or unexpected characters.
I'm not defending this, but I don't think people should be shooting down it either. It may or may not happen. Both possibilities have their own good and bad things about them.