I guess it's not impossible for a delay, but seeing how we're less than two months away, I feel like Nintendo would've said something by now. They should know if they're going to make the holiday season deadline.
How would you go about giving the series better representation? Characters, stages, items, music, etc.
Good Feel makes good music, so tracks from Woolly World and Crafted World would be fantastic. More variety with the stages would be appreciated as well.
Aside from that though, there ain't much else Yoshi's Island offers. There aren't really any "items" in the Yoshi games, so I'm not sure what Sakurai could add aside from some type of generic egg item. There's a few enemies who could work as ATs, but not many of them offer anything truly special. Those that do are probably way too niche to be an AT anyway. And as far as characters go, you've got Yoshi, the babies, and Kamek. Anyone besides them would be a stretch.