Tbh, I don't think a game like Lucky's Tale would sell well on Xbox regardless of when it releases. The audience for it just isn't there. After all, as you said, the genre isn't exactly well represented on Xbox....so wouldn't the fans of that style of game come out and buy it regardless of release date? I mean surely they'd be ecstatic to get such a platformer (if it's quality) regardless of the timing if they're so starved for it.
The truth is, it's a niche game. With the Xbox crowd at the very least. It'll sell what it sells, to those who care, and everyone else would ignore it no matter when it drops. Maybe give it a second glance in the bargain bin, if that.
No. Crackdown is the game that's likely to be murdered in this launch window, not Lucky. Lucky will do whatever it does, and it will more or less be it's ceiling on Xbox. Crackdown will be the $60 AAA game that just fades into the crowd of the holiday AAA onslaught, and largely forgotten.