The Direct will be 40 minutes and Nintendo says the primary focus will be on games releasing this winter season, but we can probably expect some stuff that'll come out within a year or so as well. Also should note that Nintendo's UK channel specifically won't be livestreaming the Direct "out of respect for the Queen's passing" but I' pretty sure people in the UK can just watch the US livestream instead.
Two of the biggest rumors floating around are 1) this might be where Switch ports of Wind Waker and Twilight Princess HD finally get announced (it's been a year since Skyward Sword HD so Nintendo won't have separate remasters battling for attention, plus Breath of the Wild 2 is likely not releasing until late 2023 at the earliest so they probably want to put out something to hold Zelda fans over), and 2) supposedly an HD remaster of Metroid Prime running on the engine Retro Studios has created for Prime 4 might be shown off and get a surprise November or December release date. If either of these rumors turn out true I'll be quite pleased, but I'm just curious in general on what we'll see since there's so many possibilities for both sequels and even new announcements.
One of the only things I think is a "guaranteed" thing to be confirmed is we'll finally get a proper date for Advance Wars 1+2 Reboot Camp (it got delayed out of it's original April 2022 date due to the war in Ukraine), and my guess is early 2023.