Launch day or launch "window"? I wouldn't bet on more than two or three first party games for launch day. For launch window, I'm hoping they knock it out of the park like they did with the Switch and have roughly one first party game a month until Christmas.
On launch day, we're pretty much guaranteed to get Prime 4 as a cross-gen game, but that's a core-oriented franchise and fairly niche. If the rumors are true that they delayed Switch 2 to make sure they have a decent supply of consoles on hand, then they're going to want a big game to appeal to all audiences. I'd bet on Mario Kart X/9/Whatever for that role. We could also see a significantly smaller effort game aimed at showing off the console's new gimmick like Nintendoland or 1-2-Switch, but even that is pushing it.
I won't try to predict the whole launch window, but I'm hoping for a good mix of returning classics, remakes (come on, KI:U), experimental new IP a la Arms, and true sequels. I think they'll save 3D Mario for their big holiday title. Some of the games from the initial sizzle reel will invitably be saved for 2025 (Monolithsoft's next RPG, possibly Splatoon 4).
It will be interesting to see how full backwards compatability affects their output though. Big sellers like Smash Bros and Animal could just get a Deluxe edition in year 1 or 2 and hold out until year 4 or 5 for full on sequels. I'm hoping it drives them to bring new IP and reserve remakes/remasters for games on older hardware like the 3DS and Gamecube. We'll see.